Hot Fuel Handling Module

[BIGJWEAVER]

I have a 87 tbi it has a fuel module under dash by the steering colum, my fuel pump quit working found the module had a bad conn. , can this be bypassed or has anyone had trouble with this and what exactly does it do, do i need it ?

[babyJay]

Can you get a pic of the back side? I bet the 3 solder joints on the voltage regulator chip have overheated and "de-soldered" themselves. Check the diodes with an ohm meter. You should have continuity in one direction, and none in the other if they're good. Those transistors could possibly "de-solder" themselves also.

I'm an electronics tech by trade, and I'm only going on the pic. I've never personally had one of these apart (yet). VR's are notorious for de-soldering themselves. You can actually get a clip-on heat sink for them. Diode failure is easy to check for. What's the number on that IC chip?

[babyJay]

pic I altered.

[BIGJWEAVER]

Baby jay the solder on one of the connectors of the voltage reg. must have overheated I think thats where I was losing it, what exactly does it do, do I need it , or can i just splice the brown and pink wire and bypass it? Its the third one over from bottom lefthand side.....

[BIGJWEAVER]

That # on the chip is a P9126-3

[babyJay]

No, I wouldn't bypass it. Just re-solder it. You can get a cheap solder iron from Hobby Lobby or a place like that for a few bucks. If I were to guess, it reduces voltage to 5 volts to run the Integrated Circuit chip. If you bypass it and run 12v+ to the chip, it will definitely let the smoke out of it. Getting all the smoke back into the chip will be no fun, and impossible.

[87chevy.com]

Ive never seen that module thing before, Ive had 2 87's, both of them I swaped engines to something else... strange module though

[babyJay]

That part # on the chip must be a trade secret with Delco. I can't cross reference it to see what it is.

[BIGJWEAVER]

JASON, I heard they only put these on heavy duty trucks v-30 duallys perhaps just dont understand what it does , before i found the solder problem i had it unhooked and jumped the hot to the brown fuel pump wire and everything seemed to work ok without it..... but if i can just resolder it that will be fine with me....

[babyJay]

Try it if you have a solder iron. Not real sure what the module does. I'm hoping someone else chimes in here.

[babyJay]

I have 2 87 30's and an 89 CC 30. where is the module at so I can look at mine?

[BIGJWEAVER]

It is located under the steering column toward the fire wall and the plug in is kinda behind the gauge cluster....its hard to find being i never knew it existed....

[babyJay]

Very bizzare. Were the other trucks you owned single tank trucks? I have one single tank and the other 2 are dual. It'll be tomorrow before I can look at mine. It's dark and 20 some degrees out there.

[BIGJWEAVER]

JASON , Ive owned alot of 80 chevys acually all duel tank and never seen one didnt even know it existed but i was fixin my oil pressure gauge and had the dash all apart and lost my fuel pump power, be tracing wires for 5 days now finally found a schamatic for a 87 that had that module on it , i traced the main feed power from pump and found it went to this mod. so i jump wire and everything started working, so i dug deeper found the mod. then found the solder problem talk about a needle in a hay stack.... drove me crazy i began to dought my mech. skills but still dont know what it does? hope somebody can feel us in......

[clinebarger]

The fuel module overrides the ECM two second timer and the fuel pump will run for twenty seconds and then shut OFF if the vehicle is not started. Its suppose to correct a hot restart (vapor lock) during a high ambient temperature condition on heavy duty models.

Heres the only diagram I have of a hot fuel module.

[BIGJWEAVER]

So is this something that you can bypass basically remove and just strait wire cause when I took it out and strait wired everything seemed to work as normal without it ?

[BIGJWEAVER]

Or should I just fix it due to vapor lock issues.....?

[clinebarger]

Originally Posted by BIGJWEAVER

I traced the main feed power from pump and found it went to this mod. so i jump wire and everything started working.

Originally Posted by BIGJWEAVER

So is this something that you can bypass basically remove and just strait wire cause when I took it out and strait wired everything seemed to work as normal without it ?

Originally Posted by BIGJWEAVER

Or should I just fix it due to vapor lock issues.....?

What wires did you jump? If you jumped the pink & tan wire that will bypass the fuel pump relay & the fuel pump whould run any time the key is on....Not a good thing.

The module going bad will not keep the fuel pump from operating like it would in a 1/2 ton truck, It just piggybacks onto the curcuit. You have another problem, The diagram I posted tells you how the curcuit & relay works. Dont worry about the module untill you get the fuel pump relay working proporly.

[BIGJWEAVER]

Thankx, to everybody for the help.....
Update....started at the fuel pump relay and tested it , it was working so I traced the tan w/ white wire all the way to the fire wall, followed it inside and pulled back the fuse box found that the tan wire jumped over to another pin splitting into two one going to the fuel module another going to the fuel pump.....
Had a bad connection on the crossover failing to provide power, removed and repaired wire.... all is well in central Fl. again.....

[babyJay]

Sweet!

[WOOS1]

Several dumb questions because I am chasing a problem that could possibly be related. Is this module only in the heavy duty trucks? Ever offered in a full sized blazer? Just looking at the schematic, it appears that that pump should have still have worked after the oil pressure came up and the oil pressure switch took over the controls?? Just would have to crank the crap out of it to get it to start (which is what mine is doing....). Sorry for all of the questions, but I am stumped on mine and trying to understand the fuel system.

[VanPedro]

Originally Posted by BIGJWEAVER

Thankx, to everybody for the help.....
Update....started at the fuel pump relay and tested it , it was working so I traced the tan w/ white wire all the way to the fire wall, followed it inside and pulled back the fuse box found that the tan wire jumped over to another pin splitting into two one going to the fuel module another going to the fuel pump.....
Had a bad connection on the crossover failing to provide power, removed and repaired wire.... all is well in central Fl. again.....

This was posted 7 years ago but I have the same issue. Wonder which connector was lose? I keep burning the voltage regulator, don't know why. No fuel no van no fun.

[johnnye23]

Old thread but info shared was pure GOLD. Thanks

[kipps]

Originally Posted by WOOS1

...Is this module only in the heavy duty trucks? Ever offered in a full sized blazer?...

Realize it's an old thread, but I've read that the hot fuel module was also added to lighter trucks that were equipped with the big block. With either the big block or heavy towing, underhood temps were enough to cause vapor lock. Hence the extended fuel pump run time.

I think this was GM's way of a work around. They could have coded the computer to keep the fuel pump on longer in the v30's and big blocks, but it would have meant stocking a larger selection of computers. This was the cheaper solution, since the engine computer didn't care whether the engine was in a v30 or not.