Intermittent Starting Problems

[Jeff G]

I have a stock 02 that occasionally cranks fine but won't start. This happen as after it has set over night or for at least several hours, in cold or warn conditions. I can go 6 mounts without it happening, then out of the blue it won't start twice or more in a couple days. This also has happened from day one.

Assuming its a loss of prime, I've always started playing with the pump and opening the top and bottom bleeds. I can always get it started after about 10-15 minutes of fiddling and cranking. Then it's fine until the next time. It never throws a code either, at least not one that turns on the check engine light.

Once it started after opening the lower bleed and allowing what sounded like air entering the filter :confused: . Another time after bleeding all the pressure off the top bleed without pumping. For all I know its an electrical problem that is only related to shaking the engine during cranking and/or time.

So I have two questions:
1) Do these symptoms ring a bell? The dealers in my area don't see many diesels and are clueless.
2) Would a device like the Preditor, with its live engine data, help me diagnose this? The dyno shop I use for my race car also claims increased fuel economy with the 40-80 Hp program. Is he blowing smoke?

Many thanks in advance. I did search old posts, but couldn't turn up anything.

Jeff

[OC_DMAX]

My first thought is that you are getting air into the fuel system somehow. The first step would to make sure your fuel filter is tight. I had a similar intermittant no-start issue and this is what the problem was. (Did this condition start after the fuel filter was replaced?)

Some additional thoughts: There should be no need to open the water drain valve on the bottom of the filter. You only need to open the bleeder screw. Most likely, the air you are hearing is not air escaping the system but rather air entering the fuel system (since it operates under vacuum).

The Predator can read some of the live data the ECM generates. As far as I know, there is nothing related to fuel system prime loss. With regard to the mileage, most of the aftermarket products advance the injection timing somewhat. This should increase mileage a little bit (0.25 - 0.5 mpg). This is usually negated by the urge to use the additional power, so the net change is negative, a lot of the time.

[Dave B]

I've been fighting a similar problem on my 03 since last summer. Cranking time would get increase. Dealership kept blaming problem on fuel filter. 3 weeks ago it left me set and they thought it was the injection pump and replaced it. It's still not fixed and the problem seems to be worse. I'm going to try the GMC dealer now. Maybe they have a better mechanic. Vacum at the test port is 3" before and after filter change. Two days ago vacum while cranking was 3" and briefly increased to 5" when it fired up and then back down to 3".

I don't think the lacal Chevy dealership requires techs to be able to fix a vehicle.

[OC_DMAX]

As stated in the other thread, the rail pressure has to rise to a certain value (don't recall the value off hand - but is something like 5,000 psi - others can chime in here) before the ECM will not allow the injectors to fire. This would be another condition for a no-start. This can be caused by a high pressure pump going bad or cracked injector bodies. I would have them check the return flow on both banks of the injectors. You could have a bad one.

[DmaxMad]

Do you have a after market alarm? I had that same problem a couple of times. My after market alarm was not deactivating the factory security system and was tripping it, not audible because the siren is wired to the after market system. The factory systems shuts the fuel off. Wait ten minutes it would crank. Next time this happens see if security is flashing on the message center when you are trying to crank it. If it is the factory security has been tripped.

[Jeff G]

Originally posted by DmaxMad:
Do you have a after market alarm? Actually I do have a Viper system for the remote start and use that as the primary lock. Once I thought I caused it by unlocking after starting the remote start sequence, but before the engine started from the glow delay.

I've also tried re-arming and deactivating both the Viper system and factory system, but this was always after it wouldn't start. So it sounds like there is a 10 minute delay that I must wait for if this is the cause.

Did you ever find a solution for this? Or do you have an unusual unlock procedure?

This sure sounds like the problem; because I've always had the feeling it was an electrical type of thing. Like throwing a switch.

Thanks to all for your help.

Jeff

[DmaxMad]

Jeff
There is a 10 minute delay before the factory system turns the fuel system back on. The alarm installer replaced the device that communicates between after market and factory system. It has not happened since that was replaced. I have a Code alarm with remote start. Remember next time it happen check to see if security is flashing on the messages panel while you are crankin it. It should not be. I took a while before we figured out what was going on. I do not have an unusual unlocking procedure. Hit the start button then disarm when ready to enter truck. This is all done with the after market remote.

[ 06-01-2005, 06:01 AM: Message edited by: DmaxMad ]