OPS failure related to fuel supply

[gofastpilot]

I just had a failure of something on my 97 6.5td w/151000.I had been noticing the last month or so that the engine would cut out for about 2 sec. while driving after a cold start.It does it once and then its fine.This week the engine started up but died 15 sec. later, got it started again and ran for 5 sec.With the key on I had fuel up to the fuel filter and IP. If the ops failed wouldnt the op gauge show failure also or are there sep. switches for each?I'm pretty sure the PMD was original.I'm going to replace the PMD first.Is it a pretty good asumption that the PMD is the culpirt?........Gofastpilot

[moondoggie]

Good Day!

I don't know about your 97, but my 95's have two completely separate circuits in the OPS. The circuit for the oil pressure gauge is one pin (the circuit is completed through ground); the remaining two pins are NO - they close when there's oil pressure. In my trucks, the gauge can read perfectly while the switch circuit is not providing power to the lift pump, which COULD cause you symptom. In my trucks, I've found that if the lift pump circuit is completely dead, the truck still runs fine until I need significant power, then it stumbles - the IP has a limited ability to pull fuel without lift pump assistance.

To check your lift pump, you might want to see my 3 June 04 post. (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=006553#000014) (Click in colored text.) There's no reason to guess about lift pump function - it's quite easy to test. Unfortunately, to test the lift pump circuit during cranking, you'll have to activate the relay some other way - the method described appears to only work for 95's (a real shame :( ). Fortunately, you could skip that part anyway - your problem seems to be when the engine's already running.

I'd bet you've got a dying FSD, but I'd check all the other things that are easy/cheap to check 1st. I think the main Page might have a really nice set of tests that More Power put together to eliminate non-FSD causes of your symptoms.

Blessings!

Brian Johnson, #5044