Removed fuel injectors, and oops.

[compleckz]

so my friend dropped off his compression tester for me to use, i pulled the #4 plug, and it looks 10x worse than it did before, it still sparks, but it must have been weak/inconsistent... i popped one of the best of my old plugs in (100k miles on them, replaced when i hydro locked), and it runs perfect.. the plug that was in there is black now, looks oil fouled like the pic in my manual, so im still gonna do a compression test, but i took it for a drive and was very pleased...

im thinking maybe the crud from the egr could have fouled the plug, since #1 and #4 are the first runners on the intake manifolds, and those were the first misfire codes i got.. maybe plug #1 is on the way out too... i hope its that, and not bad rings..

when i first pulled the plugs they didnt look very bad at all, and they all sparked...

 

[compleckz]

compression test results:
1-145
2-150
3-160
4-150
5-155
6-150

its 40 degrees, drove the truck for like 5-10 minutes beforehand.. i'd imagine the motor cooled down quite a bit by the time i pulled the plugs, and went all the way around testing.


i started with 6 and went backwards.. so i *hope* the reason 1 was the lowest, is because the battery was dying, and the engine was a lot cooler than when i started...

#2 took awhile to get hooked up, #3 just a bit less time, the rest weren't that bad, i think i got lucky on how fast #1 got hooked up.. but the time i lost on #2 made the motor that much cooler... also i kinda forgot to do it WOT, and only did 5 cranks the manual says 7 cranks.. (first test i've done, so yea my bad).. so these are with no throttle whatsoever.. manual says that the lowest reading cyl should not be less than 15psi under the highest reading cyl..

so how are my results in all reality?

 

[compleckz]

running great:

 

[MAKG]

That's a marginal result. I assume you did it dry. The spec I always heard was that highest - lowest is no more than about 10%, which is really close to what you have (and it's also really close to that 15 PSI). You can do one of two things:

1. Repeat the test with a few squirts of clean engine oil in the cylinder. If it's better, that points to a piston ring problem. If not, it's marginal valves or the water jacket.

2. Try a leakdown test. They really are much easier to perform reliably and interpret.

If you're using one of the hold-it-in-the-spark-plug-hole testers, pick up one you thread into the hole. Those are A LOT easier to use correctly. And having the throttle less than wide open can skew the results.

 

[compleckz]

dry test, threaded tester, closed throttle, 5 cranks (like 5 seconds pretty much).. i'd imagine with 2 more cranks like the book says, and easier access to air (throttle open).. it would be a lot better. is there any magic number that should be the average, or the high value? cyl #1 is the only one out of whack really, and that plug looked perfect.. i did get a misfire code on that cyl initially, but only once, and it never came back. these results don't seem like anything to worry about, it was also turning over a lot slower by the end of the test. maybe i'll go thru it again and start with #1 this time, its just a pain to hook up the tester on some of the cyls.

 

[Natedog]

so i tested the o2 sensors again, and drivers side i can only get up to .28volts.. the book says it should be between .35v and .55v..

and as i said before unplugging them does not make the truck run any different, whats the deal with that? i unplugged them during running before, and before this time, tested after like 10 minutes of the truck idling..

ALSO for some crazy reason the DPFE left side hose keeps blowing itself off...

also when i unplug that, it dosent make the truck run any differently either.

Searched Google for 'dpfe sensor ford' and found this...kinda interesting:

http://www.niehoff.com/techtips/n_sen.html

SYMPTOM: Repeated PFE-DPFE Sensor Code

APPLICATION: FORD, All With PFE-DPFE Sensor (86-94)

Ford vehicles equipped with a Pressure Feedback EGR Sensor, (PFE) or a Differential Pressure Feedback EGR Sensor, (DPFE) may experience repeated occurrence of false EGR system codes and possible incorrect replacement of components due to limitations of the factory diagnostic procedures. While the Ford "H" manual does include reference to the EGR valve as a possible source of an EGR PFE Sensor code it does not address valves that "Hang" momentarily.

Our testing has found that contaminant build-up in the area of the EGR pintle shaft, or pintle seat may cause the valves on these applications to be slow in opening when the PCM commands additional vacuum be applied to the valve. Sensing that insufficient EGR is occurring the PCM commands for more vacuum to the EGR valve. When the valve does pop open the combination of valve inertia and vacuum build-up cause the valve to over travel. This creates the sensed excessive EGR condition that triggers the false code.

Drivers complaints usually include a bucking or trailer hitching condition during shifting or initial off-idle acceleration as part of the driveability complaint, which can be especially noticeable on manual transmission equipped vehicles. EGR valve replacement is the recommended service.

A similar false code may also occur if the metering orifice located in the intake below the EGR valve and DPFE sensor is restricted. This type of problem will not create a trailer hitching condition but loss of fuel economy will be noted. Cleaning the orifice will correct this condition.

 

[Will]

Your test was done well enough to prove the engine. There are no instructions for it in the Bible or anything. You can tell a lot by watching the needle while you crank it. The needle should do the same thing for all of them--a couple giant lunges and it should be up to compression. You can also hear the air. I've never done an official leakdown test. I'm sure it's a fine thing but the compression test will tell you if something is screwed. If it is, you can hook your air compressor to the compression gauge by popping the head of the guage off--same thing you do for changing valve stem seals to hold the valves up in the cylinder. Then you listen at the intake, exhaust pipe and oil fill cap and between those three you can tell what is screwed. You compared between a cylinder that passed the test to the one that failed. It won't be good enough for publication in SAE weekly but you'll know where the problem is.

 

[MAKG]

A bit of a correction on that poor-man's leakdown test (air compressor in the cylinder). Do this at TDC/compression or you will get a false fail -- air pressure will force the piston very easily to BDC if it isn't RIGHT at TDC, and one valve is always open then. Both are always open at TDC/exhaust. There will ALWAYS be leakdown into the crankcase due to piston ring gaps. There should be no leakdown (hissing) in the throttle body (intake valves), exhaust pipe (exhaust valves), and no bubbles visible in the radiator neck with the cap removed.

There are a number of rules of thumb for compression tests. Another one I've heard is that you should get to 70% of maximum compression on the first stroke. I prefer leakdown tests because there really is only one way to interpret them.

 

[Will]

A bit of a correction on that poor-man's leakdown test (air compressor in the cylinder). Do this at TDC/compression or you will get a false fail --

I would call that a clarification. I think anyone that has the what's-it to attempt the exploration would figure that part out.

I really don't see an advantage of the leakdown test. There are no specifications for an allowable rate of leakage. The comparison with other cylinders is still a fundamental part of diagnosing the engine's condition, and the factory service manual describes the compression test, not the leakdown test. A compression test does just fine--there's not a lot of difficulty in obtaining repeatable results. The extra step is the main disadvantage that I can see. You still end up listening for air even with the rich man's leakdown tester.

I should add that the usual acceptable difference is 75%, not 90%. I've rarely seen an engine that far off though, unless it had a burned exhaust valve and was reading near zero--or was just seriously whipped in all the cylinders.

 

[97ranger4x4]

So to do a poor mans leakdown test you would get the engine to TDC and charge up the piston to 100psi and listen for air leaking? I know this sounds stupid, but how do you know your engine is at TDC?

Basically I would not be looking for a certain PSI leakage, just leakage peiord?

For a compression test, I have heard to warm up the motor to normal opporating temp.
Unplug the distributer.
Disconnect Fuel Pump relay.
Take out spark plugs, screw in compression tester and test all 6 cylinders by cranking for a few seconds.

Just want to make sure this sounds good before I do it. i have a compression tester, and I should be able to connect my air compressor into my spark plug whole with the piece from my compression tester to do a leak down tester.

Keith

 

[MAKG]

You put it to TDC on the compression stroke. There are a number of tricks to getting it right. Here's one:

Remove the #1 spark plug and put your finger over the hole. Turn the crank with a ratchet until you feel air coming out of it. Stick a screwdriver in the hole and continue turning the crank in the same (always forward) direction until the screwdriver stops moving It should correspond to the TC mark on the harmonic balancer. This TDC/compression on #1. Do your test.

Then go to the next cylinder in the firing order, remove the spark plug, and stick your screwdriver in. Rotate the crank forward until the screwdriver stops moving. This is TDC. You know it's the compression stroke because the last one was, and you're less than one rotation forward. Perform your test.

Repeat around the firing order.

You only care about calibrated leakdown for piston rings. Any leakdown at all through valves or the water jacket indicates a problem.

I find it hard to perform compression tests on a warm engine because circulating all that cool air (and evaporating fuel if you haven't disconnected the injectors) through the cylinders tends to cool them down FAST. You need to work quickly, and get it right (nearly) the first time.

Will, yes, you're right; it's a clarification.

Note that technically, you should do this test on a warm engine as well. Unless you had a valve job this morning, the valves are not truly conical, and will fit differently when cold. But I really doubt it's going to make enough of a difference for you to care. And if you happen to have a calibrated tester, the piston rings gaps are much smaller on a warm engine.