I bought a '99 regular cab with 285k. Truck runs ok, but if I step on throttle a little heavy , I get P1688 and truck cuts out for a fraction of a second then comes back.

It was less prone to this when outside temps were cold (MInnesota), now we have a warmup and it cuts out a lot.

This makes me think it could be an issue with the FPCM part mounted on top of pump, that's what the explanation of P1688 means "P1688 Internal Fuel Injection Pump Controller Failure "..

It seems to me the same issue some years ago with the GM 6.5l where the FCM was mounted on top of motor and get hot.

Anybody tried to see if it's possible to repair a VP44 by just replacing the FPCM ?

 

I did some more testing with the pump on vehicle. I am positive the fault is from the controller, not the pump itself.

If I start truck when cold and go full throttle for approx 5 or 6 minutes, I have no issues at all. When motor warms up, and probably the pump also, that's when the cutting out begins. The Hotter, the worse.

Did anybody ever tried adding a large heatsink to the top of the pump ? Or even better relocate the module somewhere away from motor ?

This reminds me of the old 6.5l issues. Practically same remedy, relocated the controller somewhere cool.

 

The VP44 has some electronics on board which can fail even though the pump is good. Mine did that (failed when hot, then cooled of and worked fine)and I still had to replace the whole pump cause nobody sells just the electronics as far as I know.

 

This got a lot of discussion a few years back. At that time it wasn't worthwhile to try to repair the electronics.

There were a lot of discussions on trying to cool the unit also, besides the cooling by return fuel. Nobody really came up with a solid solution.

I like the way you're thinking, but if there was a kit or way to help the vp44 issue it would be all over the boards and magazines by now.

The typical easy fix is a new, quality rebuilt vp44.

 

The problem when replacing the FPCA with a new one, is that it has to be calibrated with the pump, which involves very expensive equipment.


There are 4 wires attached to it and the ribbon cable underneath. We just need to find a way to extend all of them. Wires are no problem, but ribbon cable is an issue. Anybody knows how many leads does it have ? Even better, does anybody have a picture of the connector and the contacts ?