I've got an 88 d250 with 5.9L, replaced Carb with an edelbrock 600, GM hei conversion, new mechanical and electric fuel pump...however when I pull my 31ft 8200# camper for a long stretch and come to a stop it stalls out on take off. I've re-timed twice on last two hauls and nothing helps. I still lack power I think it should have but not sure if this is related. Have 7psi fuel. Truck is a bear to restart once warmed up,acts like no fuel. Any help would be greatly appreciated.

 

you got a mechanical and electric fuel pump installed on the same engine? have you check the fuel filter?

 

New fuel filter. Clear see through. Installed after realizing I was bypassing fuel through return side of old filter during startup. The electric is low psi,used more as an assist. Was having horrible vapor-lock before installing new Carb and electric pump.

 

someone told me if you have a electric and mechanical hooked up you can get a bit of a vacuum on the line which can cause symptoms similar to vapor lock. i think you have to use one or the other and see what happens.

 

I originally had only the electric hooked up and only had unsteady 2psi. Removed return line style filter and had constant 2psi. Same symptoms while towing. This is what led me to hooking other pump back up thinking I didn't have enough fuel pressure.

 

What is your actual fuel pressure now? You have told us it was 7PSI and now you say it is only 2PSI? If you can't get enough fuel pressure with one pump or the other that is a problem that must be solved but I would run one or the other and not both. 2PSI even if constant is not going to cut it when you need the extra fuel for power situations. 2.5PSI is the minimum with 8PSI being the max. All readings should be taken at the carb inlet. When you test the pressure be sure to watch the gauge when you shut the engine off as it should drop to zero slowly and not immediately.

One of the best reasons to use an in tank pump is that it eliminates any chance of vapor lock. Since you had/have an in tank pump I would recommend using it with a pressure reducer because they are only about 30 bucks and they are very reliable.

 

I have 7psi now with both pumps hooked up. Had 2 with only the electric. Will check the pressure while shutting down. The mechanical pump is off the engine. The electrical is an inline style mounted on frame rail before the mechanical. The engine only cuts out after a long hard pull...say 10 miles or so. Once I take off from a stop and accelerate it'll go about 50 yards or so and begin cutting out. I keep foot on full throttle occasionally pumping and it resumes normal lackluster operation. I would think a 5.9 with 600cfm would pull 8200# fairly easy.

 

Was the in tank pump removed or are you pulling fuel thru it?

 

SEAL i am pretty sure in 88 the 360's were all carbureted so it would not have a pump in the tank.

 

Well I'm going to re-time the engine again. Going by engine vacuum pressure. How I've always timed and I can't see the timing marks on truck to save my life. Went a little too far advanced last pull. Too far retard time before that. Going to check all plugs as well. Bought truck a year ago and haven't done anything other than GM ignition and Carb swap.