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Compression Test Results


saveatreeeatabeaver

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1996, 2.3 liter ford ranger with 207k miles on her. I recently replaced the head gasket and repaired a handful of vacuum leaks.

Symptoms:
poor idle
rough start while cold
impossible to start while warm
smell of gas after second attempt, however it could be I'm flooding it trying so much

Recent compression test showed 4 cylinders at or very near 180psi (not bad for 207k) and the fourth cylinder at 150. I'll give it a spoonful of oil shortly, however I'm curious if anyone has any advice or tests which can narrow down the problem.

Thanks,
Russell
 


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saveatreeeatabeaver

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Just added oil to the cylinder in question and I got it up to 165. Can I assume it's a valve?
 

Mark_88

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Did you do a compression test or leak-down? At 165 you're pretty close to 10% which means you're close to spec...

If you just did a compression test you may want to look into a leak-down test...a bit more accurate, but still may not clarify whether it's a valve or rings...

Rings tend to give you oil burning...but they neither of them will cause no start for the most part...unless they are really, really bad...

Edit: and I think that if you add oil and the compression comes up it is more likely rings...but I'm not thinking clearly right now...
 

saveatreeeatabeaver

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So I'll plan to use heavier oil for a while. I really don't think that 180-150 is that bad for compression, especially for a truck with 207k.

I really need to isolate the issue causing it to run so poorly and start so hard. More playing with it...
 

tcranger

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Edit: and I think that if you add oil and the compression comes up it is more likely rings...but I'm not thinking clearly right now...
yup if you add oil and compression goes up it's the rings. i don't think that is your problem. did this occur after you changed the head gasket if so check you valve timing alot of people even seasoned mechanics will get the belt 1 or 2 teeth off and it will run real poorly
 
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Duane867

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And our little 2.3's are super sensitive to timing for sure.
 

kimcrwbr1

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Did you run seafoam through it. Pull about half a can into the brake booster after the engine is up to temp and shut it right down. Let it sit for about an hour or so then start it up and run it between 2 and 3K until the smoke stops. You can put the rest in the fuel tank. Then do the compression test again and see if #4 comes up any. How old is the O-2 sensor have you cleaned the MAF. Get some MAF cleaner and then reset the computer by disconnecting the batt for 1/2 an hour. Any time you clean or change a sensor reset the computer and run it at medium speeds for about 20 mins for the computer to reset the new values.
 

Mark_88

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Did you run seafoam through it. Pull about half a can into the brake booster...
Did you mean through the brake booster hose? The OP may end up trying to dump the seafoam into the brake booster...lol...

Just thought of that thread where the guy ran the water through his engine trying to flush it...
 

tomw

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Your compression should not be a barrier to the engine starting and running halfway decent. As a matter of fact, you have very good compression on three of four, and four ain't too shabby.
You provided the following Symptoms:
poor idle
rough start while cold
impossible to start while warm
smell of gas after second attempt, however it could be I'm flooding it trying so much

You won't flood a ECM run engine easily. You have no accelerator pump to jazz a buncha gas into the intake. You can get fuel smell for a few reasons: leaking injector that dribbles whenever the fuel pump is running, ruptured diaphragm in the pressure regulator, and broken regulator that lets the full pressure apply to the injectors and leaky fuel lines.
That said, I would check the MAF for cleanliness. If it gets dirt on the tiny probes, it will give bad info to the ECM. I would also check for vacuum leaks. They will add extra air that the MAF doesn't know about, leading to leaner mixture. If you had a MAP, it measures intake manifold vacuum, and would add extra fuel because the vacuum would be lower with a leak. Take the time to check that the plug wires are installed correctly. If you have a multi-coil pack, it needs to have all the bolts installed to hold it in place as it uses them for grounds to complete the circuits. {I don't know when they went to DIS or EDIS, so if you DO have a distributor, you can set the static timing to get it running by disconnecting the plug, and, with the key 'on', moving the distributor back and forth until the disconnected plug wire, fitted with spare spark plug, shell grounded, fires.}
If you have a vacuum 'tree' on the firewall, disconnect the vacuum line from the intake and plug it to eliminate all of the other vacuum 'customer' from being a source of leakage. If that improves starting and idle, re-attach the large line, and disconnect and plug each of the other users and reconnect them one at a time to find out which is leaking.
tom
 


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