Hard FI Start after Cold Start Firing

[launieg]

I'm unsure where to start looking for the problem. If the car has been sitting a day, then I get a quick firing (as if the cold start injector is fine) and then nothing while it cranks over many times. (plug wires do spark though) Eventually, after doing this a dozen times or more, it fires up slowly and then is okay all day (even after numerous stops).

Any ideas? It would seem to be a problem with the four injectors (but not the cold start one) that clears up after a while. But I might be misreading those symptoms.

[rlux4]

Let me see if I understand you Launie. The car starts, but quits right away, and then needs to crank a while to get going. Then it runs roughly for a little while?
The cold start injector is supposed to cut out after about 8 seconds or so, does it run poorly about this long, and then quit?
Ron

[launieg]

Almost right Ron. Runs the length of time the cold start injector would be working and then quits running completely. Crank it again and each new cranking, the cs injector does it's trick (I'm assuming) so it is a repeat performance each time. Eventually (repeating this process several times)it starts firing up beyond the time of the cs injector (but roughly when it does start up for longer, much like starting a cold engine in cold weather) and away we go for the day without further troubles.

I have a feeling that the four injectors are not getting fuel for some period of time, but the cs one does (right away). That makes no sense to me, because the cs injector is at the end of the rail, and the short hoses to the cs injector and the number 4 cylinder position are about the same length and right beside each other on the rail. So why would the cs one get fuel and not the others? Or maybe the other injectors are not firing at all for some time (that makes more sense to me).

Thanks for any ideas.

[pope]

I think it could be a fuel pressure regulator problem. Sounds like it is not holding pressure, and has to build up over time.

[launieg]

Yeah, that makes sense. I'll see if I can diagnose that. Thanks. I welcome any other ideas too...

[rlux4]

You could be onto something Pope. Do you have a pressure tester to check it with Launie? The regulator should maintain about 28 lbs of pressure.
If not, you could disconnect the fuel line going to the cold start injector, (watch out for spraying) point the line into a container and have a helper crank the engine. You should get a good strong, steady stream of gas.
Ron

[launieg]

Yeah, I've done that Ron, and I do get that strong and steady stream of gas. But maybe the presssure is still not up to the 28 psi. I'll see if I can rig up a compression gauge to test the pressure. I think I've done something like that with other cars in the past (showing my age - poor memory).

[So Cal Mark]

if you don't have pressure, how is the cold start injector spraying fuel?

[launieg]

Well I agree Mark. I think the ideas was that perhapse the other injectors are needing more pressure (in total), and so that cs one gets going before the others do (but this is sounding less likely even while I type it). Frankly, I still wonder if those injectors are firing at all (for a while) and then start firing at some point. I need to get that "noid" light that Ron has mentioned. Although I think that last year I did put an ammeter on one and got a signal, so maybe I should try that again. Any other ideas?

[So Cal Mark]

you certainly need some test equipment at this point to figure out what's not working, though I doubt the theory about fuel pressure is correct. Putting a pressure gauge in line is always the first step with FI, then testing injector operation is next.

[launieg]

Okay, perhaps I can get some time tomorrow to tackle this logically. Thanks for your input. I'll let you know what I find out.

[rlux4]

My thought was that being as the cold start injector is at the end of the rail, in a straight line with the flow, instead of off a branch, enough flow/pressure might be there to make it out of that one, and not the others. ?
Has the fuel filter been changed in recent history Launie?
You can borrow the noid light set from Autozone for free, for the deposit ($20) I went ahead and bought mine.
Could it be that the injector grounds on the intake plenum aren't making good enough contact until after things warm up a little?
Ron

[So Cal Mark]

the entire fuel system from the pump fwd would have the same pressure

[rlux4]

Well, I'm going to have to concede if you're going to go and use immutable laws of physics on your side!
Ron

[launieg]

Nope, laws of physics do NOT prevail on our cars I go out today (after giving up on it yesterday) and it turns over immediately! Hard to do any diagnosis after that - just had to settle for a drive instead

Well, I'm going to tackle it sometime soon - even if it doesn't misbhehave - just so I can drive it confidently, and I'll let you know when I have discovered a clearcut problem. Thanks guys.

One thing I am going to do is get one of those fuel injector cleaning kits (the ones you hook up after disconnecting the fuel pump and blocking the return line). Has anyone tried one? You hook it up and run it through the engine (engine running) for 20 minutes, as I understand it.