[fly_yukon]

Hi everyone,

was hoping someone could offer me some advice on this:

I am changing the coil on my 1999 Yukon 5.7L and figured to make it easier I would move the wiring harness out of the way. When I disconnected the fuel injector control plug (on top of upper intake manifold, right beside where the fuel lines enter) I found that there was gas inside the plug (YIKES). Has anybody seen this before, any ideas on where to look for the leak. This can't be right or safe...help!

Thanks

Paul

 

[ChevyFan]

I'm not sure that I have a good visual of what's being discussed here. Are you sure it was gas?

 

[ChevyFan]

Any update on this issue?

 

[fly_yukon]

Hi,

Yes it was gas, just not sure how it got into the electrical connector to the injectors. I have opened the connector since then and have not seen any gas since. However, I am still having an issue with getting the truck to start when it is cold. It just cranks over and never catches. I have replaced the coil, and dist cap/rotor was done in the summer. I have GREAT spark when I pull a plug out and turn the engine over to chk. Also seems to be getting gas as pressure at fuel rail is about 55psi and I could smell gas when the plug was pulled out. Any ideas....only seems to happen when its cold out, which is often up here in Canada.

thanks Paul

 

[fly_yukon]

Oh just to add, have checked with scantool, only code set was for a O2 sensor (B1S2) that I have to change, could 1 O2 sensor cause the truck not to start at all.

 

[Davandy]

I don’ think so, the worst it will do is run on factory settings.
Have you changed the fuel filter? maybe the problem is there enough pressure but no flow.

 

[fly_yukon]

I have not changed the fuel filter....yet. However, if it was a clogged filter the pressure at the fuel rail should drop when I crank the engine and it does not, indicating to me that there is flow there. Also the problem only seemd to be present when it is cold out.

I have tried 'warming' the coil / ICM with a hair dryer but this didn't help either.

Any other ideas are appreciated

Paul

 

[Davandy]

If the engine is cold the ECU sends a signal to inject more fuel like a choke, the only thing I don't know is there a separate injector for this purpose?
Maybe you can check your manual?

 

[fly_yukon]

no cold start - update

OK, to update,
to answer Davandy, no the issue wasn't with fuel delivery. I ended up looking at all the typical values in the PCM and compared with the service manual. Found that the CMP retard value was way out of spec (should be 0-2, mine was 12), after reading manual determined that distributer needed rotating in order to move this value into specified range. I guess the distributer had been out of position for a while but in warmer weather it didn't make a difference. Once I got the CMP retard value in spec, truck starts .

However, now starts fine, but when you try going WOT the engine will chug at about 3000rpm unless you back off the throttle a bit then it will rev to maximum. Tried this with fuel pressure gauge on rail and pressure doesn't drop at all even when chugging.

I believe this to be a separate problem since all ignition related parameters are now within spec. Has anyone else experienced this 3000rpm 'chugging' when pressing accel to WOT?

BTW if anyone needs any info from 1999 C/K - Yukon Service manual let me know.

Thanks

Paul

 

[GaryL]

I had a similar sitution last month. It was on a friend of mines 99 c2500 truck (old body style) with the 5.7. He was having hard starting when it was cold and poor drivability. The fuel pressure was fine, but when I would relieve the pressure on the tester while the truck was running, it would try to die. I did the same test on my Suburban (same engine) and it would continue to run fine. It turns out the pump worked, but there was a leak in one of the lines on the assembly inside the tank. It had the proper pressure, but not the proper volume. We change the pump and all was fine.

 

[fly_yukon]

Thanks,

I will try to chk that and will post my findings,

Paul

 

[TrailLeadr]

When you're going WOT, are you driving it, or just racing the engine with no load?
Doesn't the ECU cut spark to limit RMPs to 3000 when there is no load?

 

[fly_yukon]

Haven't had a chance to check the fuel delivery issue, however, I don't think the ECU is causing the chugging at 3k RPM. I am just revving the engine in the driveway, but if I back off on the throttle just a bit when the engine starts to chug, then it will rev all the way up, so i don't think its and ECU / PCM issue.

Paul