94 4.0 stalling problem

Cooked · Aug 5, 2012

This one has me stumped..truck drives fine until i do a sudden stop and it starts stumbling. Sometimes it'll ride it out to a normal idle until another hard brake other times it stalls but wont fire up after that unless it sits for a while. only code i pulled up was 542(fuel pump curcuit).

Anyone have ideas where to start?

hilljack · Aug 6, 2012

how much fuel in the tank when it does it? inertia switch maybe or a loose wire swinging maybe grounding out.

Cooked · Aug 6, 2012

seems to do it at any fuel level. Took it for a drive around the block last night and it did it again. Thats when i pressed the schroder valve on the fuel rail and had no pressure. After letting it sit for an hour it fired right up. Inertia switch wasnt tripped but didnt investigate furhter on it. I did splice in new wire between the fuel pump and the first connector i traced it too in the hood for the power and thougth I'd do the same for ground..Can i just attach this right at the frame?

adsm08 · Aug 6, 2012

How much fuel is in the brake booster?

Cooked · Aug 6, 2012

Had the same thought about the booster..is there a way to check for fuel in there? didn't see/smell any at the vacuum hose at regulator.

shane96ranger · Aug 6, 2012

When my Mustang had the FP regulator pissing out the vacuum hole I could smell fuel in the hose for the booster. It also made the hose very brittle.

Cooked · Aug 6, 2012

ok well no gas smell in booster hose at all however the pcv tube sure smells like gas

hilljack · Aug 7, 2012

Like shane said check the fuel pressure regulator i think there is a vacum line going into it. see if there is fuel in the vacum line. also when was the last time you changed the fuel filter. as well does the engine idle adnormaly high?

Cooked · Aug 7, 2012

Fuel filter was changed a few months ago and I've looked at that vacuum hose at the regulator which looked dry and no smell. Also ran the truck and pulled that hose off am no fuel was coming out the regulator. Idle was high but have replaced the iac and took care of that. Wam idle is 600 rpm

94Reborn · Aug 7, 2012

The loss of pressure on the rail makes it sound like the inertia switch wiring or the fuel pump relay is failing. I had a mustang that wouldn't start if you tried starting it after a long driver, and sometimes the fuel pump wouldn't prime up at all. It ended up being a bad relay that would fail when it got hot.

Stinker12100 · Aug 7, 2012

I had the same problem with my 97 4.0L. Mine happened when my fuel was below a quarter tank. It ended up just being a weak fuel pump. I took the bed off and put in a new pump and the problem was fixed.

shane96ranger · Aug 8, 2012

Start it and let it run for a minute or two, then shut it off. Now go pull the vacuum line for the FP regulator and watch it for a few minutes. That's how I found my leak. It was after seeing this that I looked into the brake booster situation.

Cooked · Sep 8, 2012

Must have been a week fuel pump. Replaced and problem is gone.

94 4.0 stalling problem

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