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Flow chart.....1993.....4.9L....factory Helms manual.

I should add....you need a decent quality pressure gauge.

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Certainly not to contradict Logan but this was in the Driveability section of the 91 FSM for the 4.9, sorry about the bad copy its from my Gaxaxy S5, you see 34 - 38 psi to the extreme right

2016-05-23%2017.26.14_zpsjig1grcv.jpg

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Body yes have FSM for 92 which says the same infor as your post for me my thoughts was grounds at first but checked all points also have change both 02 sensors also apperiate your feed back logan my gauge is old school but works going to swap fuel regulator with one from bone yard and see what I have it could be a fix. From what i've read and google is what fisher say pressure should stay consited at pressure with no leak down if any but respect your input and time just grateful for help and just trying to resolve this current condition.just taking it in steps did order new orings for injectors but not at that point yet. if there's no change or inprovement with regulator going to double check vacuum again look and make sure fuel lines are good underside have replace fuel filter everything look fine no leaks. sprayed brake cleaner around injectors and vacuum no idle change while was replacing tb gasket.

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I think that a vacuum leak at an individual injector would give you a misfire not necessarily an imbalance between the banks.

Refresh my memory, are you unable to get into the DIC, to extract dtc codes? That obviously would stop you from being able to go deep into the diagnostics to perform the E046 diagnostic tree from the FSM.

So for now its best to focus on getting your DIC up and running

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Dave, a weak fuel pump affects fuel trim. Logan is correct, the fuel pressure rarely holds for very long, some do but even the ones that do, don't on a regular basis.

I would be more concerned with a vacuum leak as vacuum controls fuel pressure. If the fuel pressure is low it can cause an imbalance if the cylinders aren't getting enough fuel. Plug the return off and see if the pressure increases as indicated in Logans' flow chart.

The proper way to check for a lean condition is with an engine scope or perform a fuel enrichment procedure.

What BBF is saying is that the OBD can display O2 sensor readings and aid in diagnosing the problem. He is recommending that you have the capability to see what the Os sensors are reading first.

i'm simply saying make sure you have normal engine vacuum before trying to diagnose a fuel pressure problem

Dave what is your engine vacuum? Do you know?

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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BBF,

I think he ruled out the injector seals with the brake clean "test"...

The thing that is nagging me is the "backfire" which is usually always a timing issue. Without going back and looking I'm pretty sure he checked the timing. I keep thinking sticky valve, and when I saw your photo it stated to run top engine cleaner, I thought ......

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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no haven't rude out injector leak answering and replying to all three members with different information first and fore most thx for your time. Tech? my timing is right at specs 10 and no sir haven't checked engine vacuum I just always through when doing key on fuel pressure test it should hold pressure is what I've seen on google you tube well my pressure drops according to my fsm my pressure should be 33.4-43.5 page 6e-c2 I'm open to everyone view not trying to be argumentative at all or discredit anyone giving advice or knowledge never thought injector could leak down that fast on fuel pressure test. Heck I don't know tech it's a intake back fire I've even rotated motor TDC rotor is at number 1 pointer below is at 0 jumper a-b for timing mode to 10 degrees which is in middle of 8 and 12. Have new injector o rings coming heck if you guys rather see me try changing o rings what the heck I've done everything else almost.

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When I say timing issue, I'm saying that an intake valve is open when it should be closed if it is backfiring through the intake manifold. When it backfires through the exhaust it is because an exhaust valve is open when it shouldn't be.

One more question, did you jumper the ALDL connector while the engine was running or before you started it?

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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Yes with the key on it should hold pressure. You are seeing the pressure drop from what I gather. I think you are saying that you think you have a leaky injector. Very interesting, because that would cause your E046 bank to bank imbalance and possibly explain the backfire. A leaky injector will quickly damage your O2 sensor and CAT also. If I recall you had an O2 sensor replaced

We used to have a fellow here who was an engineer for GM, we referred to him as "the guru", I miss him. What he used to say to find a leaky injector was to lift the fuel rail and prop it up with something and turn the key to 'on' (not start) and observe the lifters for dripping.

The OBD1 system does not report misfires like OBD2. Does the engine feel like it has as misfire, does it idle rough? Do you smell fuel at the exhaust?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Haha, this thread got a little confusing, we have discussed a vacuum leak caused by a cracked o-ring on an injector and an injector that is leaking unmetered fuel. I wanted to note that.

This thread has been a little bit had to follow because there are so many aspects to it.

Lets keep our leaks straight haha

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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yes I'm little confuse plus my email grammer isn't the best there's no easy way of swaping out fuel regulator because of under side mount screw on bracket (dont know why GM did that?) with out removing fuel rail in my service manual 6E-B symptons bottom pay key on test says clearly should hold pressure which I'm not low fuel or leaking injector would cause intake back fire? back fire under load like 2500 to 3000 rpm and not all the time. Have no check light 46 appears on DIC but comes and goes Just to clear up excatly whats going on yes could be a valve like tech says I'm thinking what fisher is saying leak at injector or could be my regulator gets hung up with spring inside of unit then works. Guess what I'm going to do is change injector orings they have arrived in mail. Just not sure should i just put new injectors in or just try orings first look like would have to remove power steering resavoir alternator . once again grateful for all you guys and input here's my number can explain excatly whats going on 219 314 1854 anytime

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I had a nice phone chat with the original poster David yesterday, he is quite frustrated and he has done quite a bit of work to his 92.

He has checked and adjusted the timing, while the ALDL connector is jumped in timing mode

He replaced the TPS, EGR, Plugs, Ignition Wires, Distributor, Cap, Rotor, cleaned out the EGR flow tubes down in the throttle body, he also replaced a couple of O2 sensors. David also added a bottle of Techron to clean the injectors and fuel system.

His fuel pressure sits steady at 34, it starts higher around 38 when the key is turned on and then settles around 34. Based on what my FSM states 34 is within the range of acceptable pressure. What he needs to do is check the pressure when the engine is accelerated to 3,000 rpm, the point of his backfire.

He pulled the vacuum hose off the fuel pressure regulator and there is no fuel present. He does NOT have a hot engine starting problem, indicative of a bad regulator.

He does not have any codes that are set as CURRENT.

His problem is that, intermittently, upon acceleration he gets a single backfire around 3,000 rpm, at that point he told me that "46" flashes on the DIC. That action kind of surprised me as I never seen or heard of a code spontaneously flashing on the dash and then it occurred to me that his DTC system is probably in "SNAPSHOT" mode. I myself have never had the need to use the SNAPSHOT mode, but it appears his system is in that mode, which is pretty cool and we can infer a few things from the 46 code flashing on his DIC when it backfires intermittently, but first a few more important points,

He noted that the car sat a LONG time without being driven, (never a good thing), not good for the injectors, the odometer has approx. 45K

He indicated that he has black exhaust coming from the exhaust, indicating a rich mixture. I asked him if he smelled a fuel smell at the exhaust and he was to check.

The E046 code results from a fuel imbalance between the banks. I think that is determined by the O2 sensors if I am not mistaken, undoubtedly the temperature of the exhaust. That he gets a 46 flashing on his DIC when it backfires indicates to me that its obviously fuel related and probably an injector is leaking evidenced by the black exhaust (he also replace bad O2 sensors, a rich mixture is brutal on O2 sensors and the CAT). I am not sure what is happening at 3,000 rpm to cause the backfire, but 46 indicates and imbalance, the backfire is not likely caused by a sudden vacuum loss, its more likely caused by too much fuel entering the cylinder causing the backfire.

The problem at this point is finding the leaky injector. The guru used to say to lift the fuel rail and support it so you can see all the injector tips, turn the key to the ON position to pressurize the injectors, and observe the injector tips for any dripping, replace that injector.. I would imagine that a power balance test could find the problem injector but I am not 100% sure of that, the plug fires, its just that the injector is over fueling and I am not sure that would be obvious in the power balance, as much as a misfire condition would. This is OBD1, unlike OBD2, OBD1 does not set codes either general P300 or specific cylinder P30x, so finding a leaking injector is more difficult, although I am not sure that a leaky injector would create a misfire condition. One thing you could do, was to pull each plug and examine it, a plug in a rich environment will have a black sooty appearance and it will look different from the other plugs. Here is a link to info on visually examining spark plugs, http://www.4secondsflat.com/Spark_plug_reading.html

Here is an interesting spark plug analysis chart, see Carbon Fouled, you will note that its caused by a rich mixture. Pulling the plugs and laying them side by side sort of like in a police lineup, the culprit may be obvious!, and you found the leaky injector.

spark_plugs_diagnosis_zpscxcedhdj.jpg

Is there anyway to find a leaky injector other than lifting the fuel rail?, anyone?

David said it looked to him that he needed to remove the power steering pump to lift the fuel rail, its been a long time since I worked on a 4.9. Can someone recall if that is true, do you need to remove the power steering pump to lift the fuel rail? I need to get my pool open asap, or I would pull the FSM. OldCadTech? Does the power steering pump need to be removed to pull the fuel rail? And, I recall, there is a quick release fitting on the pressure side of the pump, any info on that would be appreciated. I remember struggling with that fitting to get it to release. Special tool needed if I recall?

While the fuel rail is up, David can replace the injector O-rings and replace the regulator if he likes. David DO NOT attempt to clean the injector tips or touch them. One more thing, a leaky injector washes the oil off cylinder walls and can potentially damage the rings or walls, in addition fuel can get into your oil.

I hope that focuses this thread a little better, any suggestions or ideas much appreciated.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Sat for a long time - but is it driven now and not simply bad gas from sitting undriven?

That is a good thought, David what is the status of the fuel?, was it flushed?, have you been through a few tanks?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Thank You BBF for clarifying the symptoms :hatsoff: I was going to call Dave but my schedule is so crazy right now, there was not enough hours in the day. It's taken me days to put this together and modify as the information came in. There is an easy way to determine which bank is running rich by looking at fuel trim counts but I would have to look at a service manual to refresh my memory on fuel trim counts. I need to know if the black smoke is still present at 3000 rpm. The test "The Guru" referred to was an easy and valid test, to raise the fuel rail and check for any leaking injectors. Daves' problem could be an injector that is not shutting off entirely but I'm not sure I would recommend this test for someone with limited experience as there is a high risk of fire involved. No offense Dave but I've seen experienced techs start fires.

The problem could all be determined and pinpointed to a particular cylinder by a trip to an engine scope before any disassembly. He was using the car for road trips if I recall, so I doubt if it is stale fuel.

Dave - you need to do the tests and determine the true cause of the problem not just replace suspected parts, even cheap parts. Stop that.

I would think a miss at 3000rpm would likely be caused by a dirty injector holding the pintle open. The only way to correctly diagnose the injectors is to use an injector tester. Dave, call around until you find someone that has one and knows how to use it.

An injector O-ring kit should come with all the seals needed including fuel line replacement seals as well, but don't discard any seals unless you are sure you have a replacement for them.

If you do need to remove the fuel rail.... You don't HAVE TO remove the fuel rail entirely but it is the RECOMMENDED procedure to minimize the possibility of damage to the fuel rail.

FUEL RAIL REMOVAL:

Before removal, the fuel rail assembly and intake manifold may be cleaned with a spray type engine cleaner/degreaser, prior to removal. Remove any loose debris prior to removal.

CAUTION:
^ DO NOT immerse fuel rails in liquid cleaning solvents.
^ When servicing the fuel rail assembly, be careful to prevent contaminants from entering the intake fuel passages. Fittings should be capped
and holes should be plugged.
^ Support the fuel rail to avoid damaging components.

1. Disconnect the negative battery cable. Recommended...
2. Remove the air intake assy from T-body.
3. Relieve the fuel system pressure, refer to your service manual.
4. Remove engine belt and P/steering pump bracket and reservoir mount bolts and Lift/Move the power steering pump assy. Do NOT remove lines, no need...
5. Disconnect the vacuum line from the pressure regulator and base assembly.
6. Disconnect the accelerator cable, cruise control cable and bracket.
7. Disconnect the electrical connectors from the TPS, ISC, CTS and MAT sensors.
8. Remove the coolant hose to thermostat housing.
9. Disconnect the fuel feed line from the rear fuel rail assembly. Discard the O-ring.

10. Disconnect the fuel return line.

IMPORTANT: Wrap a shop towel around fuel lines to collect fuel.

11. Disconnect the EGR vacuum lines from the EGR valve.
12. Remove the five rail support bracket bolts.
13. Disconnect the electrical connectors at the front and rear fuel rail assemblies.
14. Carefully, Remove the fuel rail assembly from the intake manifold.

FUEL INJECTOR REMOVAL:(Fuel rail removed)
1. Disconnect the injector electrical connector while the fuel rail is inverted.
^ Push in the wire connector clip while pulling the connector body away from the injector.
2. Remove the retainer clip from the injector.
^ Spread open the clip slightly and slide the clip away from the fuel rail.
3. Remove the fuel injector assembly.
^ Twist back and forth while removing.
4. Remove the O-ring seals from the injector and discard.

FUEL RAIL INSTALLATION:

NOTE: Lubricate new injector O-ring seals, I like to use clean transmission assembly lube or petroleum jelly.

1. Install the fuel rail assembly to the intake manifold.
2. Install the five rail support bracket bolts, and tighten to 24 N-m (18 lb. ft.).
3. Connect the electrical connector at the front and rear fuel rail assemblies.
4. Install the EGR valve and vacuum lines.
5. Connect the fuel feed line. Use a new O-ring. Lubricate the O-ring.
6. Connect the fuel return line. Use a new O-ring. Lubricate the O-ring, and using a back-up wrench to prevent damage, tighten both the fuel feed and return lines to 30 N-m (22 lb. ft.).
7. Connect the coolant hose to the thermostat housing.
8. Connect the electrical connectors to the TPS, ISC, coolant and MAT sensors.
9. Connect the accelerator cable, cruise control cable, and bracket.
10. Connect the vacuum line to pressure regulator and base assembly.
11. Install the power steering pump.
12. Install the air cleaner.
13. Connect the negative battery cable.
14. Energize the fuel pump and check for fuel leaks.
15. Perform the IDLE LEARN PROCEDURE, refer to MAINTENANCE PROCEDURES/IDLE LEARN PROCEDURES.

As I stated above I've modified this several times as more information came to light, so if it seems to be somewhat erratic I apologize for that.

s-l225_zpsr34wwjfw.jpg

Edited by OldCadTech

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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Hey!, a fire would have solved his problem! :fireman: The guru never mentioned potential of fire. I do think he recommended someone turn the key on however while someone watches for a drip...

So you have him going to a shop? "The problem could all be determined and pinpointed to a particular cylinder by a trip to an engine scope before any disassembly"

Come on OldCadTech, that's no fun.. :D . if that is the case, pull the plugs and line them up and see if one looks like it is black. And yes, I think the SNAPSHOT will show fuel trim, and THAT should direct you to a specific bank, so you would only need to pull 4 plugs and line them up, black plug, pull the injector.

David, OldCadTech is going to show you how to pull up the SNAPSHOT and look at fuel trim if its do-able. The procedure is in your manual also. I believe you have saved SNAPSHOTs for the 46 code.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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LOL :paint2: -- "but I would have to look at a service manual to refresh my memory on fuel trim counts​" Seems I remember something about lower trim counts are rich conditions because the O2 sensors read oxygen blah, blah, blah but it gets pretty fuzzy after that and I don't have the code books to help get into trim counts or snapshot data.

I might be able to dig something up on line though.... but..... since he is going to take it to have it scoped, I won't need to :P:) :)

You being a NS man, you are thinking the plugs are easy to remove like a NS and they are on the left bank but the right bank - NOT so much --- You're spoiled ....

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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Hey, I am no GM tech but I always thought doing the plugs on the 4.9 was easy, but I am 6'5" and I get up on the engine and mount it! :wub: Plus I have hands of a surgeon, no seriously hands of a surgeon and a terrific sense of touch :ninja::ph34r: The only thing I ever worried about were the screws sticking through the firewall that would cause a nice cut on the back of your hand, once that happens you wear one glove.

Now in the old days I ran into engines, Chryslers, chevys and cadillacs that NEVER had the rear or plugs behind generators, changed. Hands of a surgeon

Now the NS plugs will cause your blood pressure to rise., the rear needs the ignition module removed, its a mess, I prefer the plugs on a 4.9. The last set of NS plugs I removed it felt like I was removing the threads with them, I swear someone used either honey or molasses to lube the threads it was tight all the way out...scary

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Hey, keep in mind that I was my parents pit crew on their 59, 62, 64, 65, 66 and 68 Caddys every weekend they took 400 to 800 mile trips for their work, in those days plugs came out every 10,000 miles to be re-gapped, but you know me, I gapped those 45s's every trip they took for extra performance and pop. On the assembly line, I would be the PLUG GUY, :blink:

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Dave,

Very important question...

Did you jumper ALDL terminals A&B after the engine was running or before you started the engine when you set the base timing?

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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It's been awhile and I have forgotten the details.....but the export cars had a odd display mode on the IPC. Code 46 being one of them.....and it being different than the ECM code 46.

Could be the IPC is from a different year or configured wrong. Code 46 and the backfire may seem related....but it may be 2 completely different things.

See attached image

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2003 wasn't THAT long ago

Found one of my posts....from 2003....different site. 2003? ....really?

http://www.cadillacforums.com/forums/cadillac-seville-cadillac-eldorado-forum/4139-46.html

Bruce

2016 Cadillac ATS-V gray/black

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