Compression Test and then some - Ford Powerstroke Diesel Forum
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Old 06-14-2012, 06:23 PM Rookie

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Compression Test and then some

I have read several threads on posts regarding compression test.
The way I have performed these tests in the past is to:
1. Get engine to operating temp.
2. Relieve all cylinders. Meaning if it's gas remove spark plugs and if it's diesel remove all glow plugs if applicable, and all injectors if the former is not.
3. Perform compression test
4. I prefer results to be within 10% of each cylinder on a street engine and no more than 5% on performance engines. (I actually was even more anal when I worked on competition engines)
There are times that you may have to perform a compression test on an engine that is cold. I refer to that as a whistle test. If done properly it will reveal information, all beit other than statistical not worth much.
What are your opinions, ideas, etc.
I just performed a compression test on my 7.3 that laid down on me a couple of weeks back today.(I don't trust garages)
Everyone had ideas what was wrong but nothing definitive.(I don't pay for ideas) I got my truck back home and have just started working on it.
Between my computer and my knowledge I believe I have a PCM/Harness issue. I am going even further though because my truck has almost 300K miles on it and 17 years.
This is what I know for sure.
1. I have 3 injectors that are not healthy
2. I have issues with engine oil pressure.(didn't occur till the girl laid down. I didn't realize it, she had been telling me but I didn't listen. My Bad. That is for another post.)
3. There was an issue with the PCM connector
4. I believe I have a problem with the wiring harness on top of the engine.
I believe I know why the ole girl just died. (previous post)
I am going to perform some PM's now, I figure the shop that looked at her wanted over $5500.00 to possibly fix her that I can do alot more with the same money.
Anyway, I know this is long winded, I think a good discussion on compression test was needed. I also am open to any suggestions on things to do.
The following is what I am doing this weekend:
1. Oil cooler rebuild
2. replace all injectors with new
3. replace hpop
4. replace lpop
5. replace IPR
6. replace ICP
7. replace EBP sensor and tube
8. possibly any other ideas y'all might have
Thanks, Vince
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Old 06-14-2012, 09:43 PM
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what year is your 7.3l don't want to do the math. i'd recommend replacing your under valve cover harnesses too as those are famous for causing injector issues. but sounds like you have a long weekend ahead of you
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Old 06-15-2012, 05:15 AM Rookie

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'96 F 350 Crew Cab 4x4
The under valve cover harness looks good as do the feed throughs. I did have one of the external connectors going bad again though. I had replaced them a couple of years ago and the driver side front is just starting to burn again
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