Need help with a 3.9

Big-Pig · Mar 25, 2016

I have a 1993 D150 with a 3.9 that wont start. I replaced the in tank pump with a frame mounted pump and now it shows good pressure at the rail, but does not seem to be getting any fuel through the injectors. I also check and i am getting power to the injectors.

1) I dont have a check valve. Do I need one?

2) What else could keep the injectors from working?

Update: I'm getting 50psi at the regulator.

Big-Pig · Mar 25, 2016

update: ITS RUNS!!!!!!!! :roflsquared:

Turns out, you really need a fully charged battery to open the injectors. However, I still would like some opinions on the check valve.

crazzywolfie · Mar 25, 2016

if everything is working properly you should not need a check valve in the line. i would also not put much faith in that frame mounted pump. they are really not meant for daily driving

Core-Lokt · Mar 25, 2016

Agree on the external pumps. Unless that's something altogether different from the usual ones, those were intended as a booster pump for vehicles with weak mechanical pumps or relocated fuel tanks.

If you're going to try running it as-is, at least compare the volume/pressure ratings to the stock pump.

crazzywolfie · Mar 25, 2016

Core-Lokt said:
Agree on the external pumps. Unless that's something altogether different from the usual ones, those were intended as a booster pump for vehicles with weak mechanical pumps or relocated fuel tanks.

If you're going to try running it as-is, at least compare the volume/pressure ratings to the stock pump.

it is not even that. they are just very prone to overheating and dying when used on a daily driver. there is a reason they use in tank pump on all fuel injected engines. i don't even see why someone would install and external pump on a vehicle that had a in tank pump from the factory. a new stock type fuel pump is not that expensive but i know the aftermarket external ones are usually pretty pricey.

also you shouldn't need to worry about pressure or volume. there is a fuel pressure regulator on the engine.

Core-Lokt · Mar 26, 2016

Understood about the pressure regulator on the engine, but the aftermarket pump might not have the volume and pressure equal to the factory set-up if it's one of those assist pumps.

I think you're dead-on about the heat soak. I could imagine being stuck in rush-hour traffic and having the heat soak from the pavement underneath, ambient summer temperatures and vehicle operating temperatures.

crazzywolfie · Mar 26, 2016

an aftermarket pump should be more than powerful enough to keep up when working properly. electric fuel pumps are not usually meant to assist. they are usually meant to work alone. running more than one pump on a line can possibly cause a fuel pump to burn out even quicker.

Big-Pig · Apr 11, 2016

The fuel pump I used is a Bosch unit for a 1993 thunderbird (i think). I am a little concerned about heat, but this truck has a history of eating fuel pumps. I believe the wiring is a factor and I will be rewiring it from the battery before I tag it. I let it sit with bad gas and the injectors and regulator got gummed up. Before the regulator opened up the pump was pushing around 80 psi, after it was free it sits at about 40 psi. After i tag it, I plan to drop it a few inches and post a video on Youtube.

Need help with a 3.9

Big-Pig

Junior Member

Big-Pig

Junior Member

crazzywolfie

Senior Member

Core-Lokt

Senior Member

crazzywolfie

Senior Member

Core-Lokt

Senior Member

crazzywolfie

Senior Member

Big-Pig

Junior Member

Similar threads

Latest posts

Staff online

Members online

Forum statistics

Share this page