f250 probs

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Aug 2, 2011 | 12:36 PM

msckksm

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f250 probs

I have a 1990 f250 diesel, the oil pressure gauge drops to zero when the check engine dummy lght comes on and I also notice the rpm gauge does not stay up it drops to zero as well . What is going on?

Aug 2, 2011 | 01:00 PM

powerstroke72

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Moved to the Pre-Power Stroke Diesel (7.3L IDI & 6.9L) forum.

Aug 2, 2011 | 01:11 PM

Phy

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Did these symptoms start at the same time? Recently?
It sounds suspiciously like an instrumentation/wiring problem, though my tach did that & was the tach sender...
I'd check the cab ground strap first. Lotsa weird things can happen with a bad ground...

If you don't find anything obvious, I'd try to get a mechanical oil pressure gauge to install temporarily & verify the oil pressure.

Aug 2, 2011 | 01:16 PM

msckksm

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250 probs

I do not know if the problems are connected just noticed them. The main problem is the oil pressure gauge takes a dive only when the check engine light comes on. I will check grounds and electrical first Thanks, Mike

Aug 2, 2011 | 01:46 PM

GHeTTo JOe

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i think the check engine might come on when oil pressure is less than ~7??

Aug 2, 2011 | 06:15 PM

IDIDieselJohn

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Don't rely to much on that gauge anyways..... there borderline useless!

Aug 2, 2011 | 09:45 PM

tecgod13

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Quote:

Originally Posted by GHeTTo JOe

i think the check engine might come on when oil pressure is less than ~7??

Yup, I want to say thats the ONLY time the check engine light will come on in these trucks. So the check engine light is doing what its supposed to do if the oil pressure gauge drops to 0. Generally speaking, the gauge is just a fancy looking idiot light for most of these trucks. The sender is just an on or off at 7 PSI or so. Some of the earlier trucks with 6.9L's had real pressure senders, but the later trucks were switched to on/of senders.

Seeing that the tach is dropping at the same time, I'd say check the grounds, and other wiring under the dash and see if anything might be rubbing or shorting out.