Injector Pump Diagnosis

[harrietnorth]

Looking for a good tech article to walk a diagnosis for an IP. Saw the sticky in tech articles with the stanadyne db2 and the trouble shooting didn’t seem to line up with my issue.

Truck starts great. Idles fantastic. hot or cold. Gets up and goes down the road like it’s supposed to. Except in the last week...
Verified that the fuel system is leak free, no fuel in the valley, recently (last year) replaced all the return orings, caps and lines.

Symptom: under medium acceleration, say between 3rd and 4th, when you run up the rpms to ~3k, press the clutch let off the accelerator, shift to 4th, engine has no power. Won’t rev above 2k. Cycle the engine, all is good in the world, until you dump rpms to the next gear again.

Was intermittent, now it’s pretty consistent. Worse when it’s hot out.

My understanding is there is a pressure release valve inside the DB2 that when engine speed swings from high rpm demand to low allows the pump to equalize the fuel pressure in the pump back to static, and that this can get stuck or start leaking.
Valley is dry, no fuel weeping, no noticeable smoke black or white.

My instinct says failing IP.

Thoughts? Previous Owner states pump replaced 6k ago and I have no reason not to believe him.

 

[Thewespaul]

Are you running an electric lift pump by chance? I’ve run into this issue with some customers running my pumps with an e pump and no regulator, with over 10 psi it floods the transfer pump and makes it difficult for the metering valve to compensate. And just because it was replaced doesn’t mean it was a quality rebuild.

 

[harrietnorth]

Are you running an electric lift pump by chance? I’ve run into this issue with some customers running my pumps with an e pump and no regulator, with over 10 psi it floods the transfer pump and makes it difficult for the metering valve to compensate. And just because it was replaced doesn’t mean it was a quality rebuild.

Still mechanical lift pump. Looks new.

Agree on the IP.

 

[Thewespaul]

You can try and run a heavy dose of fuel cleaner or atf through it and see if it helps, but it likely needs to come apart

 

[harrietnorth]

You can try and run a heavy dose of fuel cleaner or atf through it and see if it helps, but it likely needs to come apart

What’s the best way to give the IP a good dose? Pull the filter, add ATF.

 

[Thewespaul]

That works well, I would start with that and then do a triple dose of your favorite fuel cleaner and run a few tanks of fuel through it, it’s not likely going to be something that instantly fixes itself, but more of a slow improvement if anything