PMD or lift pump?

[rapidoxidationman]

A couple of weeks ago my truck stalled at a stop sign, but started back up easily enough then ran rough for a couple hundred feet then was fine until today. Cruzin down the road it started to feel like someone was turning my ignition on and off (dash guages and lights said otherwise) and a minute of this later it quit. I popped the hood to look for anything obvious, wiggled some wires under the intake manifold, started it back up without a hitch, and high tailed it back home - no sign of trouble during those 20 miles. Sounds like a pmd yes? Another bit of info: My lift pump hasn't sounded as smooth as it used to. Any thoughts and info would be appreciated.

Regards,
Rapid

[bmjjm]

Rapid,
My experience with the fsd is that when it quits, it quits, no advance notice. Another thing, the lift pump is a heck of a lot cheaper than a fsd, and a whole lot easier to change. My truck is a '94, I wired the lift pump up to a switch inside the cab, solved a lot of problems. ( I firmly believe they had some wiring issues back then, my truck, and about ten others that I know had serious wiring issues. When I blow the horn, my headlights come on) Just be sure if you do re-wire the lift pump that you wire it to the key switch, not direct. I know, I know, if it rolls over, and the motor stalls, the lift pump will still be pumping fuel, and it creates a fire hazard. To be blunt, if I roll it over, I've got more serious issues.
Hope this helps,
Bill

[Barry Nave]

FSD will do this. When it cools a little it will start up though the stalling will get to the point it's done.
This has happened to me a couple of times.
The truck will run with out the lift pump under light load. A test of the lift pump would be to run at idle then open water bleed vavle.Truck dies lift pump gone.
Also with Eng running you should be able to feel the pump run as will as hear it.

[bigcontender]

You can check the lift pump pressure @ the water separator drain hose with the truck running. My 96 run 10.5 psi which I told is very good can't tell you what the minumim is. It's an easy check.

[rjwest]

1. change the cheapest thing first.

2. install fuel pressure gage, easssier to diagnose filter/lift pump vs pmd/inj pump.

[rapidoxidationman]

Thanks for the replies everyone. I'll try to test the lift pump tomorrow and am considering the following unless otherwise advised: start the truck and pull the pump power relay under the hood - simulate a bad pump by shutting it off. I know it's having issues by the intermittent noise it makes; hopefully this is the problem. By the way, would a bad fsd/pmd throw a code and light up the SES light on the dash?
Thanks,
Rapid

[KallyI]

rapidoxidationman, my pmd failed like that this past summer. I now keep a spare with me, because that was the 3rd time. My lift pump failed, and it just didn't have quite as much power as it should, but it didn't quit on me. Just my .02 cents worth.

[Barry Nave]

The two FSD I had to replace did not gice any codes.

[BUZZ]

A lift pump likely doesn't stall the engine. A failing PMD behaves the way you describe. You should regularly check for proper lift pump operation due to starving the IP for fuel, and shortening the IP life.
Make sure you check your grounds, fresh fuel filter and such.
What code set?
Buzz

[rapidoxidationman]

Buzz,
no codes were set, seems like a pmd would trigger one but the posts above say otherwise. Is there any field test for a pmd? It's kind of an expensive part to just be throwing a new one in and hoping it fixes it...
Thanks,
Rapid

[scotts]

I am having similar problems with my '95, 270Km's. I will be driving or sitting at a light and it will stall. Some times it fires right up, other times I need to wait 30 sec. It seems better in cold weather (below freezing) by better I mean it doesn't stall as often. I have noticed that after a 2+ hour drive and I shut it down that when I fire it up again 1+ hours later, it will stall more often.

I had some problems driving on the highway on the weekend. It hasn't stalled in a while, but then it stalled about 5 times. It also almost stalled but kept going about 10 times. The lift pump seems good, I am thinking FSD :(

One more thing, it doesn't like to run/idle around 1500-1700 RPM, runs very rough like when a carb is opening the 4bbl's too soon. Any help would be great as the weather is only going to get warmer.

[rjwest]

Scotts, from my limited experience ( see previous
reply , this post ). I would suggest doing
cheapest/easiest things first.

1. FUEL. Must be clean and in cold weather not
gelling up: FIlters, Sample fuel inglass jar,
Drain water , Again. Add inline filter

2. check lift pump pressure, I added a fuel pressure gage in cab, No more guess work....Is this original lift pump, ? Oil pressure sw, 1995-94

3. You may want to check wiring, but most lickly not pproblem

4. How old is IP and FSD

5. Remote the FSD with new one, if not problem you have a spare and will likly need it some day.

6. Now it is probably the IP, Mine had a
slight miss at 1500-1700 for 30k miles before
I had same stalling symptoms....

I only had a code once. inj pulse to short.