PAUL T Posted July 6, 2009 Author Report Share Posted July 6, 2009 UPDATE! I am still having the same problem with the 97 Deville, there are 126,000 miles on it now. P0171, P0174, P0151 all intermittent usually occurs at idle while stopped in traffic, after I clear the codes they may not come back for a few days. Hard cold and sometimes hard warm starts. I even think the starter relay is going bad from all the hard starts. Sometimes I get just a "click" like the relay does not want to kick in, almost like it does with a dead battery, but after a few more turns of the key it starts cranking. I did put a new FPR on the other day and no change. I have checked vacuum hoses again with no luck. I hooked up the fuel pressure gage and when the key is on, engine off, it goes to 20#, after startiing it goes to 32# and holds. I did put a new(made in China)fuel pump relay on back in January and I thought that fixed it but it did not last long. I was not happy with the "made in China" quality so I am thinking about ordering a new GM one from Rockauto. I even checked and cleaned through the air box to the throttle body and cleaned the throttle body, to no avail. The car runs fine after it starts, even after the codes come up it does not even stumble. I also checked the evap system for carbon buildup but found none. I am going to look on my 94 Concours to see if there are any relays the same and try that route again. Mileage is staying around 16 to 18mpg. Any other suggestions? Link to comment Share on other sites More sharing options...
BodybyFisher Posted July 6, 2009 Report Share Posted July 6, 2009 32 psi sounds low, mine is 42 psi with the key on and 42 with the engine running, when I turn the key off, it holds pressure and drops to 10 psi in about 2 hours 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 Link to comment Share on other sites More sharing options...
Texas Jim Posted July 6, 2009 Report Share Posted July 6, 2009 UPDATE! I am still having the same problem with the 97 Deville, I hooked up the fuel pressure gage and when the key is on, engine off, it goes to 20#, after startiing it goes to 32# and holds. Any other suggestions? In my opinion... I think the low fuel pressure at KEY ON..ENGINE OFF..is what is causing your hard starting issues. 20# of pressure will not open the injectors. 32# will just barely do it. I think the fuel pressure is supposed to be somewhere around 40# of maybe a little more. Link to comment Share on other sites More sharing options...
Ranger Posted July 6, 2009 Report Share Posted July 6, 2009 I'm with Jim & Mike. Your problem is the fuel pump. 20 psi is WAY to low. Link to comment Share on other sites More sharing options...
PAUL T Posted July 6, 2009 Author Report Share Posted July 6, 2009 I just ordered a Geniune GM fuel pump relay from Rockauto. I will try that route first before I put the new fuel pump on. I always thought a weak fuel pump would crap out pretty quick and not linger for 10 months. The only other thing I did notice was that the hose going from the purge solenoid to the vacuum switch (refer to the picture in post #36) there are red fittings in the hose I removed that line and I could not blow air through it. I checked the fittings and they appeared to have some kind of valve or a restriction in them, I checked the hoses and there were no restrictions. Is there supposed to be no restrictions in that line? I think I will have to inspect that further also. Link to comment Share on other sites More sharing options...
BodybyFisher Posted July 6, 2009 Report Share Posted July 6, 2009 I had an additonal thought, the P0174 shows a lean condition, low fuel pressure would trigger that. When you change your fuel pump could you start a thread, Id love to see your procedure, I have a bad fuel level sensor and at 127K, I think its time to replace my pump 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 Link to comment Share on other sites More sharing options...
PAUL T Posted July 7, 2009 Author Report Share Posted July 7, 2009 I had an additonal thought, the P0174 shows a lean condition, low fuel pressure would trigger that. When you change your fuel pump could you start a thread, Id love to see your procedure, I have a bad fuel level sensor and at 127K, I think its time to replace my pump Before I change the pump I will report on any change when I put a new fuel pump relay on. The last fuel pump I changed was years ago on my wifes 88 Cutlass Supreme Classic. I backed it up on ramps and used a 2 ton floor jack to let the tank down slowly after taking off the straps. Then I changed the pump reconnected everything and jacked it back in position tightened the straps and done. The Cutlass is still running so I must have done it right. I have also had the tank out of my 1969 Corvette, it developed pin hole leaks so I had it welded. I primed and painted it with several coats gloss black paint before I reinstalled it. Now that I am older I am not as excited to work on them as I used to be, it seems like Murphy's law comes into play more. Link to comment Share on other sites More sharing options...
PAUL T Posted November 11, 2009 Author Report Share Posted November 11, 2009 New fuel pump solved the code problem. Low fuel pressure was causing the codes. Since the new pump, no codes. I ended up paying someone $70.00 to change it because I just could not get the time. Link to comment Share on other sites More sharing options...
BodybyFisher Posted November 11, 2009 Report Share Posted November 11, 2009 New fuel pump solved the code problem. Low fuel pressure was causing the codes. Since the new pump, no codes. I ended up paying someone $70.00 to change it because I just could not get the time. Glad to hear the good news, this is an interesting thread. I like this thread, it shows 1) how logical the NS system is, and 2) it shows how methodically this board attacked the problem. There are many threads over the years where this board has collectively analyzed a problem and come to a successful conclusion and this is one of them, Paul, I would like to close this thread, as sort of completed at this point. What do you think about that idea? What happens from this point usually is that the thread carries on, and members diagnosing problems add stuff like, MY STS is doing the same thing, bla, bla etc, etc, etc....muddying up the beautifully to the point thread.... I will check with Bruce first to see if it can be REOPENED in case YOU want to open it to update the status, etc... but what do you think? Paul, if I were you, since you were able to illicit a slight improvement when you swapped the starter relay, I would consider changing/replacing that relay, it is possible that the bad starter motor increased current draw causing the relay contacts to overheat, burn, pit, etc.... Initial closing of the contacts would experience the most load stressing the contacts if the draw were high. Great thread, very informative and valuable 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 Link to comment Share on other sites More sharing options...
PAUL T Posted November 11, 2009 Author Report Share Posted November 11, 2009 I found this thread again when I was looking for your "oil light" thread. I always try to find my old threads that were left unanswered and conclude them so people searching can see the end result and not just wonder what happened. I have no problem with you closing this thread. I will probably switch out the starter relay for peace of mind if anything. I have still not ruled out a bad new battery in this case though. I plan on having it load tested if I have anymore problems starting. I will post results of that on the other starter thread. I am amazed at how good the car runs now that the pump has been changed. Before the change I was getting these codes and others that relate to low fuel pressure on a daily basis. It is so nice to not see any codes since I had the pump done. Thanks for the kind words. Paul T. Link to comment Share on other sites More sharing options...
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