Coming home from work Firday, pulling up a pretty good hill in 5th at about 55mph, tuck just died. Coasted off to side of road and it restarted fine - saw no leaks or anything obvious. Drove about another 5 miles and when slowing down to turn, at idle, truck died again. Restarted, but kinda felt like it was missing as I got RPMs up to 1800RPM, let it come back to idle and it died. Changed fuel filter on side of road, re-started fine, felt better - no missing at higher rpms. About another 5 miles and it died at about 1200 RPMs in 5th. Restarted and made it home - about 2 miles. Been gone since then and haven't had time to look at it more. Hoping it's just the lift pump. Forgot to mention - on that stretch home before it died the last time - I was hearing a kinda of clicking from the engine. No gauges or anything to see lift pump pressure at this time. Just go ahead and install new lif pump??
Thanks, Duke

 

When mine did the same thing the problem was the overflow valve.
Try it first.
You won't find valves any cheaper than here, most places will charge twice as much

Precision Diesel Injection and Turbo Inc.
Marty Tompkins
888-734-7349
$35 + $7 shipping and handling.

 

Thanks for the info. I hate to be dumb, but exactly what is the overflow valve and where is it? Is it just a recirc valve for injector pump?
Thanks, Duke

 

Another question - after searching through other threads, looks like these overflow valves from Marty are kinda "clicky" - are there better ones, or is it even a concern?
Thanks, Duke

 

I've never had a problem with the dozens of Marty's valves I've installed. Piers http://www.piersdiesel.com/ sells them for around $55, Cummins was about $70 several years ago, Dodge wants like $160.

The OF regulates the pressure to the injection pump and is the single most often part to fail on a 12 valve engine. They just wear out.

5 minute one wrench job to replace if you don't lose the washers. Only trick is that on some trucks the valve hits the manifold before it will come out.
Don't bend the line to make it come out, you'll have a heck of a time getting it back in the right place. Instead file or grind the cutout on the manifold till it comes out. Doesn't take much.

Object at lower left is the oil fill cap

 

Great, Thanks!!
Duke

 

"Clicking" to mean points to lift pump.
I would do the overflow valve first. It should be replaced if you have to change the lift pump anyway.

Stopped at local diesel shop a couple weeks back. A 98 12 valve had just gotten a major service and they were going to bump the plate a bit for more hp.

Truck ran fine, but when loading on the dyno a loud clicking started. Did the sound test and determined lift pump. Installed a fuel pressure gauge and it confirmed the sound check. Everytime it clicked, the fuel pressure went flaky. Gave it a dyno load test and fuel pressure dropped to 10 psi.
Installed a new lift pump and everything was good.

 

I replaced both the lift pump and the overflow valve on mine and still clicks as loud as ever.

 

Thanks for all the input. I ordered an overflow valve from Marty today, supposed to be in Tuesday. He said he thought it still might be a lift pump, too. Guess we'll see. I'll start w/ the overflow valve, and go from there. Thanks, Duke.

 

When my 91 ran flat and died like yours, it ended up being a hole rubed in the feed line half way from the tank to the lift pump. The line runs right along the frame, and dirt lays there to set up corrosion. Never did leak fuel to let me find a wet spot, but every time it died, the filter was half full. Worth takin' a lokk, alot cheeper than a pump!!!

 

I hate to say it, but it sounds like an internal injector pump failure. Seen it several times, the clicking comes right from the governor, and is caused by wear inside the pump. Seems to be most common on 94's from what I've seen.

 

so internal pump failure means....just opened up this one and wadded up rubber washer with scattered aluminium, could that mean internal failure? what coulda caused that?

 

Only cause I've seen for blown out internal pump seals is when people stretch the overflow valve spring without a fuel pressure gauge and jack the pressure way up. More is not better.
Repair is a rather uniform $1200.