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injector problem?


SteveK

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Well, I'm at a loss. I have a '97 Deville (base) and I've done just about everything I know to fix a hard cranking problem. Once the car sits for over ten minutes it takes several seconds of cranking to get it started. Once started it runs like a champ. However, I have noticed a 2-3 mpg drop over the last month or so. Anyway, on a previous forum it was suggested to change the fuel pressure regulator. I did but this did not fix the problem. The fuel pump was checked and has good pressure. The only thing left to check (I know of) is one or more leaky fuel injectors. First, can anyone think of anything else that might be causing the hard starting condition and the drop in mileage? I have the following codes: P0138, P0151, P0154, P0171 and P0300. Second, if I do have to check the injectors what is the best way to check them? I was told to leave them on the rail and simply lift them up and look for a dribbler. Is there anything to watch out for? If I do this will I need to replace the o-rings on the injectors no matter what? It would be nice if I could take it to a Cadillac dealer and say "fix it" but I was laid off and don't have that kind of $$$$$$. Thank you all in advance for any insight you might have. Sincerely, Steve Keitel

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Well, I'm at a loss. I have a '97 Deville (base) and I've done just about everything I know to fix a hard cranking problem. Once the car sits for over ten minutes it takes several seconds of cranking to get it started. Once started it runs like a champ. However, I have noticed a 2-3 mpg drop over the last month or so. Anyway, on a previous forum it was suggested to change the fuel pressure regulator. I did but this did not fix the problem. The fuel pump was checked and has good pressure. The only thing left to check (I know of) is one or more leaky fuel injectors. First, can anyone think of anything else that might be causing the hard starting condition and the drop in mileage? I have the following codes: P0138, P0151, P0154, P0171 and P0300. Second, if I do have to check the injectors what is the best way to check them? I was told to leave them on the rail and simply lift them up and look for a dribbler. Is there anything to watch out for? If I do this will I need to replace the o-rings on the injectors no matter what? It would be nice if I could take it to a Cadillac dealer and say "fix it" but I was laid off and don't have that kind of $$$$$$. Thank you all in advance for any insight you might have. Sincerely, Steve Keitel

P0138 - Heated Oxygen Sensor (HO2S) Circuit High Voltage Bank 1 Sensor 2

P0151 - Heated Oxygen Sensor (HO2S) Circuit Low Voltage Bank 2 Sensor 1

P0154 - Heated Oxygen Sensor (HO2S) Circuit Insufficient Activity Bank 2 Sensor 1

P0171 - Fuel Trim System Lean Bank 1

P0300 - unspecified misfire

The first thing you need to do is to get rid of the O2 sensor problems, replace them with KNOWN GOOD O2 sensors

Also find out why you have the P0171 lean code in bank 1, that is due to a vacuum leak or from being starved from fuel

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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Steve you didn't mention it but has the fuel filter been replaced? I've had this same issue but only during cold starts (below freezing) several moments of crank and nothing but then after about ten minutes it will pop and Misfire then start and run all day like there was nothing wrong in the morning. Anyhow check that out if not already done. It's below the drivers rear door :)

Sean M.

1997 Cadillac DeVille

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I feel your pain. I just fixed my 8 month hard starting problem on my 97 Deville. My fix was a weak fuel pump. It was not pumping enough pressure and gas mileage suffered. Double check the fuel presure, it should be at 42-45#. I went from 15MPG before to 20MPG after. I was also getting the same codes as you are, I even changed one O2 sensor to no avail. How old are your plugs and wires? Check for a vacuum leak. Check for a plugged pcv valve. Check/change fuel filter. Eliminate the easy stuff first. I see you have posted your problem before http://caddyinfo.ipbhost.com/index.php?showtopic=24097 and I gave you all this information back then. Here is my thread. http://caddyinfo.ipbhost.com/index.php?sho...t=0&start=0

Read up and good luck.

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Steve you didn't mention it but has the fuel filter been replaced? I've had this same issue but only during cold starts (below freezing) several moments of crank and nothing but then after about ten minutes it will pop and Misfire then start and run all day like there was nothing wrong in the morning. Anyhow check that out if not already done. It's below the drivers rear door :)

I thought about this also, but he said he had normal fuel pressure, so I assume it was checked cold to make sure the pressure came up with the KEY ON position and the fuel relay has been eliminated as a source of trouble

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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Misfire code P0300

Connect a vacuum gage. On most vehicles a normal reading is 17 to 21 inches Hg. If the needle is lower, is jumping up and down or steadily dropping, you have a vacuum problem. Look for possible vacuum leaks by checking vacuum hose connections, the throttle body and manifold, and PVC valve and plumbing. An EGR valve that is leaking can also act like a vacuum leak and cause a random misfire. The next thing you should check is the fuel pressure with a gauge. If it is not within specifications (refer to a service manual for specifics because fuel pressure is critical for proper engine performance), the problem may be a weak fuel pump, low voltage to the pump (check the relay and wiring), or obstructions in the fuel line (like a plugged filter). A bad fuel pressure relay can also leak pressure and prevent an otherwise good fuel pump from delivering full pressure to the injectors. Dirty injectors can also restrict fuel delivery and cause a lean fuel condition.

See this thread, it was the fuel pump if I recall, Paul had similar symptoms to you

http://caddyinfo.ipbhost.com/index.php?showtopic=19656

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 Paul I see you posted above before I posted a link to your thread, the fuel pump fixed your problem, I wonder who checked the fuel pressure. If I recall without going back to your thread your pressure was low

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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first of all, thank you all for your input. I did replace the fuel filter but have not checked for a vacuum leak or done a fuel pressure test. My mechanic did these tests, or so he says, but to be honest I can't get a direct answer in terms of numbers so I doubt his work. Sorry to be so stupid but where would I get a vacuum guage and where should I connect it to the car? I had the injectors cleaned a fewe months ago along with the fuel filter. Also, where do I connect the fuel pressure guage? I will check all the things you all have suggested and get back to you. Thanks again! Steve Keitel

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I posted about the vacuum gage before I ran across and recalled Paul's fuel pump problem. Buy yourself a fuel pressure gage from Sears, it screws on to the schrader valve on the fuel rail. The first thing I would do is check fuel pressure, keep in mind that Paul went a long time with low fuel pressure, when the low pressure was finally identified, I was surprised as to the problems low pressure could cause but the engine still run

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 Paul I see you posted above before I posted a link to your thread, the fuel pump fixed your problem, I wonder who checked the fuel pressure. If I recall without going back to your thread your pressure was low

Yes my fuel pressure was low and it did last alot longer than I thought it would (13 months) before I had it changed. What Steve has sounds exactly the trouble I was going through. Steve, you can pick up a pressure guage from Sears as Bodybyfisher suggested or you could go to about any auto parts place and get one there or just borrow one from somebody who is mechanically inclined that would have one. I got mine form NAPA for $40 or $50. The schrader valve is located on the fuel rail on the front of the engine on the drivers side under the beauty cover, it looks like a tire pressure valve with a cover on it. As far as a vacuum guage, you might not need it, just check for a hose with a bad connection or a hissing sound or any hose unhooked or out of place.

Edited by PAUL T
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Gentlemen,

I have done some more checking. First, I do not have any leaking fuel injectors. I purchased a fuel pressure gauge and tested the pump. When I hook up the gauge and turn the car on the pressure reads 44 pounds. When I start the car the pressure drops just for a split second to 38 pounds then holds steady at 40 pounds. Paul T mentioned that the pressure should be 42 to 45 pounds. Is that turned on or engine running? If that is running could a difference of 2 to 5 pounds cause the hard starting condition? I have cleaned just about anything that involves the fuel or air system including the fuel lines, throttle body, IAC valve and the egr valve. I have replaced the fuel filter, air filter, battery and the fuel pressure regulator. I only use high-test from reputable gas stations. I don't know if this matters but I live in Denver. Is there an altitude adjustment I need to make? I could not find any broken or cracked vacuum lines (doesn't mean there isn't any). If I have to replace the fuel pump do you know if I can remove/replace from my trunk or do I have to drop the tank? Thank you all for your help!

Sincerely,

Steve Keitel

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This comes from the GM SI, based on this, your fuel pressure appears to be low

With the ignition switch ON and the fuel pump running, the fuel pressure indicated by the fuel pressure gage should be 333-376 kPa (48-55 psi). This pressure is controlled by the amount of pressure the spring inside the fuel pressure regulator can provide.

A fuel system that drops more than 5 psi in 10 minutes has a leak after the fuel pressure stabilizes in one or more of the following areas:

The fuel pump check valve.

The fuel pump flex pipe.

The valve or valve seat within the fuel pressure regulator.

The fuel injector(s).

Fuel pressure that drops-off during acceleration, cruise or hard cornering may cause a lean condition. A lean condition can cause a loss of power, surging, or misfire. A lean condition can be diagnosed using a scan tool. If an extremely lean condition occurs, the oxygen sensors(s) will stop toggling. The oxygen sensor output voltage(s) will drop below 500 mV. Also, the fuel injector pulse width will increase.

A rich condition may result from the fuel pressure being above 376 kPa (55 psi). A rich condition may cause a DTC P0132 or a DTC P0172 to set. Driveability conditions associated with rich conditions can include hard starting (followed by black smoke) and a strong sulfur smell in the exhaust.

A lean condition may result from the fuel pressure being below 333 kPa (48 psi). A lean condition may cause a DTC P0131 or a DTC P0171 to set. Driveability conditions associated with lean conditions can include hard starting (when the engine is cold), hesitation, poor driveability, lack of power, surging, and misfiring.

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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I would say that your fuel pump is starting to get weak. What BBF wrote is right out of the manual. Anything below 48# ,pump running engine off, will cause all your problems. The pressure I told you I think was on my 94 Concours. Rockauto.com had a good price on fuelpumps. Yes the tank has to be dropped to replace the pump. Do not do like I did and wait a year to change out the pump, do yourself a favor and change it now. I ended up having starter problems.

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Ok, I will replace the pump within the next week or so. Now, how difficult is it? I have the "directions" but really, can the average backyard mechanic do it in their driveway or should I pay $225 in labor and have it done? I don't mind trying it to save some money but I don't want to screw something up and wind up costing myself more money.

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my pump died on my 96. dropped tank which is no fun. the electrical leads had green corrosion which i have read about. changed pump assy since i did not want to do it later down the road. i took apart old pump and it worked fine. $5 wire harness was almost surely the problem but since it is attached to pump, the tank had to come out.

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