Hello all, have a 99 Vert with 6200 original miles on it. Car has performed well enough with exception of the drivers side door locks going out. But that was fixed easily enough with new relays. Anyway!

My problem started about 2 days ago, the car always used to crank three times and then start and I was pretty good and used to that so I would release the key. The first time it happened I didn't think anything of it the engine wasn't started right away but burbled to life without me having to turn the key again. Over the past couple days things have gotten progressively worse to the point where it takes two 3 - 4 sec cranks to get the car started where just a couple days ago it took only one 2 sec crank or so. There is definately something wrong.

My first instinct is that the fuel pump is going. Perhaps the old owner let the car sit with gas in the tank and no fuel stabilizer. So my first order of business is to buy some injector cleaner and see if that clears things up.

If it doesn't... does anyone know the proper procedure for checking the fuel pump to make sure it is producing the proper pressure?

I'd rather not drop the tank as I am sure it is a 'in-tank' pump withouth knowing for sure that its bad. Any other suggestions as to what the problem might be would be welcome.

P.S. The car runs fine once it is started with no signs of hesitation, surging, or lack of power. Also I thought it could be the coolant temp sensor not readining right and therefor the ECU no enriching the mixture enough on cold starts. However I tested that today and while the car starts fine if you shut it off and start it a minute later, the car has the same above problem if let sit for maybe an hour or so. At that point the engine and coolant are still very warm so I don't think that would be the problem.

Thanks for all your help guys
-Eric

 

Have you ever changed the fuel filter? I believe that the pressure regulator and the fuel filter are one assembly. I recall when the fuel pressure regulator when bad in my 00 silverado, it would crank a number of times before starting.

 

Nope never changed the filter. I suppose it is not a in-line filter? Could you please tell me where the filter and regulator are located? On the car?

 

The fuel filter/pressure regulator is located under the car on the left rear side. There are two lines going into it and one line coming out.

 

Check for DIC codes to see if there are any that may point to a cause.

My car has been doing this on and off. It will occasionally crank longer and then not-so-confidently catch, then run fine. If I hit the starter momentarily, then back off, then hit it normally, it would start right up.

After checking through all the possible likely causes and finding no problems. I changed the battery because it seemed to be having problems getting above 60% charge, then added some fuel system cleaner, but the problem seems to be somewhat still there.

I do believe the issue is with the PCM based on the sensor readings. It reads several sensors including the IAT and ECT sensors, and if these sensors are more than 5*F apart from each other it could cause a problem. I tested both sensors and they appear to be fine, but before I start my car I check the ECT temp on the DIC, and the Outside Air Temp on the HVAC display. Even though the OAT sensor is not the same as the IAT, it should give a reasonably similar reading as the IAT. I do find that when the starting is a bit harder than normal the ECT and OAT readings are more than 5*F apart. The ECT sensor seems to read dead on during normal driving (190*F during normal highway driving).

I'm not overly worried about it at this point, but I'm watching it. The fuel system cleaner seems to be helping. Also, I think there's more ethanol in the summer gasoline blends, and if you don't drive your car that often the PCM doesn't adjust quickly to the change.

 

Can anyone expand on this some more? I have not pulled codes yet but I have a similar problem - on the first (cold) startup after previously driving in heavy rain, my car will turn over, catch, then immediately turn itself off. Starts fine on the 2nd crank, but won't start on the first. Something to do with 'moist' air? I was also wondering about PCM temp or humidity readings also.

Thanks fellas.

Smash

 

just a thought, and a shot in the dark.

How old is the gas in the tank itself? I had a C4 with fairly similar problems on starting.

2 common solutions was bad gas .. and a fuel pump and/or filter
I wound up draining the tank, running a full tank through with an additive (forgot what the name was) to remove possible water.
helped a bit .. but not completely ...

replaced the inline filter ... no help.

Finally the pump/filter in the tank.

That finally solve that issue .. again on a C4 not a C5. Not sure how diffrent they might be atm ... but sounds very similar

 

do a fuel psi test look at the readings when you first turn the key not on 2nd try look for it to hold psi after ya turn off. should not drop more than 20 lbs in 20 min.

 

Will be doing the pressure test tonight hopefully, just picked the gauge up on lunch from work but still have classes to go to tonight. The GM tech said I should be looking for 55psi static with just the key on. Your saying no more than 20psi drop after turning the key off and letting it sit for 20 min? Just confirming... Also do I leave the gauge connected during this 'hold' period? I would assume that I do.

Hopefully I am just having alot of fuel pressure droping when the car is off. And hopefully its the flapper valve in the fuel filter not the tank/pump. The filter is onlt 60 bucks, GM pump/sending unit is over $500, after market walbro pump is like $230. Just more money than I want to spend.

Anyway thanks for the help, I will post results.
-Eric

 

Ok Tested with the fuel pressure gauge.

Turn on the key, I get 60psi right off the bat, but pressure instantly drops very very rapidly. When the car is running pressure reads 60 psi steady.
Pressure will drop to about 10psi with the engine off.

So what do you guys think? Bad fuel filter check valve? Something else?

 

Lots of owners on this Forum are experiencing the same thing, including me. Do a search on this forum and start ruling out the obvious stuff first.

I'm still having the starting problem you are and I've run through a long list of things to check, all so far are OK. I haven't taken it to a dealer because I have a custom PCM tune for a H/C set up.

 

yep its the check valve. if you repeat the test a few times you will see it hold psi. dont go after market go gm [pump/sender]. or live with it

 

Replace the rear fuel feed pipe. It has the check valve incorporated into it. Your pump is fine.

 

Yeah I know the pump is fine, I was going to replace the fuel filter/pressure regulator as GM tech said there were two 'check valves' one in the fuel filter and the other one either in the pump or somewhere else in the tank. You say the rear fuel feed pipe? you talking from the pump to the filter? can you give me a little more info about where it is in the system?

 

It doesn't matter. I think BOTH of them should be replaced but that's just me. Replace the regulator/filter assembly first. It could be "leaking down" on it's return side. If thats the case don't worry about the in tank check valve.


(this is a major reason of WHY I use chevron/unocal(76) gas exclusivly). They fiilter at the pumps better then cheaper stations.

 

i think the rear fuel feed tube in only on 97-98 models...you can find it on left rear tire removed hard to get to but has a check valve inside it about 3ft long ....good luck

 

And you know this how?

 

on an 01 check valve is part of pump assembly. mine used to start with just a touch of the key and i mean a touch. like the starter would never wear out and i didnt like it in winter i like a little cranking pre lube first. well i got my wish i have to crank a full second or release and recrank then it fires right away. i tested and found it wouldnt pass key off holding psi first time,it holds all other times . just sitting over nite, im not gonna pull the tank it doesnt bother me that much.

 

1997-1999. The check valve itself is incorporated into the line and is not inside the tank. This line begins at the fuel tank, then branches. One leg (the one that goes to the fuel filter) continues to the fuel filter and the other leg branches off and connects to a hose going to the right side fuel tank.
HTH,
Robert

 

Same for 2000.