I had to wait to get a fuel pressure tester from Mid America to go to the next step of this diagnosis. Again, the engine cranks great but will not start on first turn of the key in the morning, but at lunch time it will, -most of the time. I have started to wait for the pressure to build by turning the ignition key, and then waiting until the warning chimes finish before turning the starter. On the first turn of the starter, it just will not start, even if I crank it 10-15 seconds. Second crank, it fires, regardless if I really crank it a lot the first time, or just a tiny tweak of the starter.

The pressure goes up to 58 psi with the key to ignition, no stater, then in about one minute will loose about two (2) psi. It continues to drop but it would appear to be a slower drop after the first minute. If the ignition is on or off, it doesn't matter, the pressure drops off at the same rate which is about a psi every 30 seconds.

I have already ready replaced the fuel filter with an OEM AC Delco filter towards fixing this issue.

I pulled my limited restriction dual cotton cone air intake system and replaced it with a stock paper filter. I broke down the MAF and cleaned the MAF filiments with denatured alcohol.

Does this still point to the rear fuel feed hose? Or does this smell like something else?

Thanks,
Bluemill

 

It's beginning to sound like another animal to me. That kind of fuel pressure is fine and is plenty for starting.
My particular problem was the pressure dropping off very rapidly after the fuel pump stopped running.

 

I've got the same problem right now (and had it when the car was 2 weeks old)... The dealer replaced the fuel pump assembly when it was a month old and the problem was solved.

Looks like I need another fuel pump...

There is a check valve that is likely allowing fuel pressure to leak back into the tank...

In my 98 is was part of the fuel pump assembly, but I believe there is also a check valve in the fuel feed rear line...

Good luck

BBEngineer

 

Judging from the fuel pressure being generated (58psi) and the fact that it is bleeding off very slowly, I'm not as sure. I'm almost tempted to look into fuel injector(s) or spark plug issue, or both, on this one.

JMHO

 

Well I've never done anything to the plugs, the're original with 35,000 miles on them. Any recommendations?

 

It wouldn't hurt to check the plugs, but I doubt if they are the problem. At least you could see if you're dealing with some sort of humongous plug gap though.
From your description of what you've looked into, it still sounds to me like something fuel related. The 58 psi is good pressure and the slow bleed-off doesn't seem to indicate a rear fuel hose check valve problem.
Try running a full container of Chevron Techron through each of the next two tanks of gas. Use the large size that says it is "for up to 20 gallons". Maybe one or two partially clogged injectors here.

Anyone else care to offer their thoughts here too?

Robert

 

I have a 2004 Z06 w/ 17000 mi and have started encountering the same problem. Got a couple of charge system faults, replaced battery w/ excide orbital thinking this was the cause, start problem seemed to diminish but not go away. After reading this post I started thinking that the fuel system being a single pipe and if the check valve does not hold the fuel leaks back into the tank, when the car is being started fuel pressure can increase but have no real fuel to be delivered to the injectors, when the key is turned the second time the fuel is now at the injectors for the car to start. During the reset of the day there is not enough fuel loss through the check valve so the car starts properly. This is just an possibility.

 

Just out of curriousity, should there be any bleed off of fuel pressure as I stated, about 1 psi every 30 seconds for the first couple of minutes? I think Gonzo might be thinking the way I am, or at least it makes sense. It may not be a completely shot rear feed hose check valve, just one that's starting to weep, like a water pump starting to drip, before it's really gone bad.

I'm in the midst of changing plugs. I am going with AC Irridiums (41-985(?)). The old plugs look like they have an enormous gap, (41-952) and so far all have a light gray deposits on the tips. That #7 plug was a tough job, burried tight to the power brake booster. I have small hands and it was difficult to pull the boot off without yanking the wire. I measured about 345 ohms on all of the left bank wires. I will do the other side tommorrow.

I have been running almost 100% Shell premium, which is a top tier fuel with super anti-deposit additives. I know every top wrench I know swears by Techron, and maybe I should run a biggie bottle of that through as you recommended "LoneStar". You notice I say almost 100% Shell, well it's like 3 out of 4 tanks are Shell, the 4th is no name premium- just because the gas is so Damn expensive lately.

 

Bluemill: Any update on your issue? I've been seeing the same issue for the past few weeks, and it's interesting we're in the same part of the country.

• In the morning, the car will crank longer than normal and not cleanly fire.
• If I back off the starter, sometimes it will actually catch as the starter stops.
• If I hit the starter with a quick tap, back off, then start it as normal, the engine will fire right away.
• When the engine is warm (sitting less than 4 hours) it starts fine.
• I also use Shell V-Power almost exclusively.

Not a voltage/battery issue (just changed the battery last weekend to an Exide Orbital).
Possibly high ethanol content in the gas?
MAF and IAT check out OK. No codes.

 

my 01 coupe used to start by just hitting start position. i realy didnt like it cause in winter i would like a little oil crank time. but every once and awhile [cold] it cranks much longer and second turn lites off. i'm lazy and did not want to drag out my fi psi tester but thanks you did . youre psi is ok what i would do next or you do it [i'm still lazy] get a 'NOID" . DISCONNECT 1 INJECTOR wiring connector and put the noid in connector . if a spark tester is handy nows the time or pull 1 plug wire and insert a good spark plug then lay it on engine metal [ground] get someone to crank it over . hopfuly it wont start the noid should flash and you should see spark across plug. use nothing but a noid you can fry something if you try a test lite . some GM systems shut offfuel if they dont detect spark.

 

I know what I'd do...

When you are certain your C5 is at the condition where it will not start the first time.... before trying that first start - I'd remove the airbridge and get someone to squirt starting fluid (or gasoline) directly into the throttle body during the first cranking session.

If it starts/trys to run, then you know for certain that it's a fuel problem.

Fuel pressure meters will register on compressed air as well.
If all the gasoline is returning to the tank after a long sitting spell - then when the pump is turned on, the pump will try to fill the empty line - it will compress the air (now) in the line - and cause a reading on a fuel pressure gauge. You may get a decent reading... but it may not be because of gasoline in the line... but compressed air.

.

 

Not a bad idea Mike, plus this is something easy to do. On the compressed air in the line thing, most of the fuel pressure gauge testers have a purge valve that relieves fuel pressure (at least mine does). I might try hooking the gauge up, turning on the key (engine off) to read the pressure, then depress the purge valve to see if air or fuel is coming out. Worth a shot.

 

i just went throught the exact problem ..mine was the rear fuel feed hose...remove wheel on left side and 125.00 later ..problem fixed..is was not my fuel pump....on the 97 and early 98 they had this same set up.....it has a check valve inside it ...had changed almost everything else before this.......this was my problem oh..my fuel pressue dropped quickly after keyed pressure up...

 

real fast go no go test . in engine bay r/s in front of batt. UNDER HOOD FUSE BLOCK ASSEMBLY remove star nut and cover there are 3 grey relays all have same part #. ID. ignition relay and swap it with any one of the other 2 . try to start it. be advised if cured you put a so so relay in the cooling fan slot . ya got me unlazy i swaped mine this am. car fired right off. i'll try it for a few days

 

Well, it looks like I've got the same problem!.....My "google" search brought me here....

2004 Coupe, 27k miles (all mine), only run Chevron 91-93 octane fuel, all the time, with a bottle of Techron every 3 months.....

at 25k car used to start with only a "blip" of the key....now, after sitting overnight, takes at least 3 seconds on key before light-off....

After reading all the posts, this appears to be a common problem?....

I've still got warranty, so I'll be dropping it off in a couple of days....

 

the o4 pressure check valve on made on the fuel pump

 

i swapped relays this am. lit right off but a few more days will tell the tale. the pain in the but is ya have to hook up a lot of test equip. ,leave the hood open and hope that it has the morning key sickness that day. ya cant hold the key cranking and yell to some one hey putz check fuel and spark

 

Thanks for the relay tip. This weekend I'm going to check a few theories as well regarding the grounds for the ignition system. Interestingly enough there's a common ground (G106) that's common to several ignition related components... including the Ignition Relay! I think we're on to something.

 

Probably not check valve related.
The car will start just fine even without the check valve, as long as it's within the 2 seconds that the fuel pump is still running after first turning the key.

 

may not be the ground but always check. this relay powers 4 mini fuses ign. inj. oops 5 fuses tac,ing/inj,ing/inj,a/c,and tcc. with a helper ya can put a test light on any of those fuses while cranking.assuming you have power to relay while cranking. i,ve seen more relays go bad than ign. switchs i,m a retired self employed mechanic. you guys have made me dig out alot of service books looking at wiring diag. etc. kind of felt good trouble shooting again. i always prided myself on electric repairs.