... the engine runs perfectly and accelerates well at full power. I didn't really think the fuel filter would solve the issue, but I learned awhile back to work my way up from cheapest possibility. I think I'm looking at an electronic issue, unfortunately probably the pcm or maybe even a fuel injection issue. Either way, it's starting to look like I'm going to have to get some outside help for the girl.

 

Goodmorning Jack;
Personally I would say, that if it's an electronic issue, it is doing it's job or not, and not a bit, that's why I think in mechanical troubles, but, maybe I'm wrong, and when I am, then I've learned something again!

looking forward to what the solution was!

best regards Ton

 

any easy, or only moderately hard checks for this?

 

Goodmorning Jack (I suppose it's morning there; here it's 1730hrs)
Jack, there is a ventile on the right side of the pressure pipe(top front engine) which suplies the fuel to the injectors. When you have left your truck for a couple of days, you should turn the startkey , that your can hear your pump and immediately shut off the contact. Your pump has built up some pressure and when you open the ventile , probably air comes out. then you know that the fuel runs back. That's the way I should investigate it.
An other possibility is, that the membrane in the fuelpressure regulator has a little hole and that the fuel runs back to the tank thru the overflowline.

Let me know what you found , if you like

best regards ton

 

I went ahead and replaced the fuel pressure regulator since that was next on my list of relatively inexpensive possible culprits. The truck started right up after changing it out, but very rough - as if out of timing- with very little power for several minutes. I checked vacuum connections and found no problems, so I turned the truck off. When I started it back up it ran like a champ. Now it seems to be doing much the same thing as before. I have spark and I have good fuel pressure but either something in the pcm is hindering the fuel injection or something mechanical is hindering fuel delivery. Today is very humid, and this seems to be a consistent cause for this problem. I'm going to check the relay for the pcm next -- is there a mechanical component to these relays or are they solid state?

 

I replaced both pcm and fuel pump relays on the off chance... - no dice. Getting power to pin 1 on the pcm/eec wire harness so no issue there. Still getting good spark on crank. As I understand it the pcm/eec controls the fuel pump on turning the key on it should run for only a second or two, and when it fails to advance to start the pcm should cut it out. I have good fuel pressure from both tanks and spark. I have to assume I'm not getting signal to the injectors - which also leads me back to the PCM/EEC - or all of my injectors have simultaneously failed. I replaced the PCM 2 months ago because the old one burned, but the truck has been wonky like this for most of the time - getting progressively worse. Is it possible for the PCM to fail intermittently? Once the vehicle starts it runs great, and it will start immediately when the fuel pump stops properly when turning the key to the on position. Hate to take the part back and scream warranty if it's not the PCM, but I'm 'bout out of other possibilities. Any ideas/suggestions will be greatly appreciated

 

Still didn't post the fuel pressure...

 

these are the things I've done so far:
1. replaced burnt pcm/ecc two months ago
2. after wonky starting behavior became bad I replaced fuel filter thinking I had a mechanical fuel delivery problem.
3. replaced the fuel pressure regulator.
4. realizing the fuel delivery problem must be electronic in nature I replaced the relays for PCM and fuel pump.


Diagnostics:
1. inexact test, but very hard fuel spray at schrader valve on rail
2. power on pin 1 of pcm harness
3. checked & cleaned all ground points.
4. problem is FAR worse on rainy days and bad on very humid ones - to the point where I don't even try to start it when it rains.

 

whether or not the pressure is at 40 - 50 the pump(s) should still cut off when the key remains in the on position if the pcm is operating correctly, right?

 

We need to know the fuel pressure. Can't help you without it.