bad compression

Topic: bad compression (Read 2859 times) previous topic - next topic

bad compression

October 10, 2013, 02:18:16 PM

i discovered a few months back that fuel was getting into my oil i found that an injector was leaking so i replaced the injectors changed the oil and fuel was still getting in the oil i then ran a compression test and found that the two cylinders on the outside are just below 90psi and the two in the middle are just below 140psi and it appears that its got a small leak at the front of the valve cover could this be causing my low compression

bad compression

Reply #1 – October 10, 2013, 03:23:45 PM

Valve cover leaks wouldn't effect compression. If you have low compression on two cylinders next to each other I would guess a small head gasket leak.

bad compression

Reply #2 – October 11, 2013, 01:29:00 PM

theyre not next to each other the cylinders wth bad compression are the two on the outside their seperated by the two in the middle

bad compression

Reply #3 – October 11, 2013, 02:25:16 PM

squirt a little oil in the low cylinders and retest if it comes up chances are its in the rings if not then it probably the head or head gasket

bad compression

Reply #4 – October 11, 2013, 11:57:46 PM

Anytime you test a cyliner WET the compression will come up. This is not a correct way to test it. Leak it down for true test results.

bad compression

Reply #5 – October 13, 2013, 07:51:21 PM

so i did the leak down test and air was only coming out of the oil fill just barely i then decided to do another compression test this time i used a friends tester and all cylinders were 150 so i guess mine was broken but i still dont know how im getting so much fuel in my oil the only thing i can think of is the adjustable fpr but i dont know how to adjust it

bad compression

Reply #6 – October 13, 2013, 09:57:23 PM

run codes.

bad compression

Reply #7 – October 14, 2013, 03:09:55 PM

Go buy you or borrow an EFI fuel pressure tester and check the pressure at the schrader valve on the fuel rail. I don't have the specs handy but I'm sure you will find the correct fuel pressure somewhere on the internet or in a manual. ALSO, since the car has an adjustable fuel pressure regulator, which I assume is aftermarket...you havent said what engine you're running... you should check and see what fuel injectors you are running and make sure you have the right injectors for your ecm/tune. A previous owner may have stuck in some 19 or 24lb injectors in a SO engine...and speed density computers cant handle that. Trust me I have a 351 with ported GT40 heads, a typhoon intake, headers, free flowing exhaust, a bigger SD friendly cam and 1.7RRs running on 24lbers with a 460 ECM (which is set up to handle 24s) in my F-250...you have to have the right ECM or tune to handle different injectors.

bad compression

Reply #8 – October 14, 2013, 04:15:15 PM

he has the 2.3 me think.

running codes should always be the first step. could be un-metered air, o2 sensors, timing, all of those things should show up in the 2 mins it takes to pull codes.

bad compression

Reply #9 – October 14, 2013, 04:21:22 PM

Fuel in the oil is caused by a couple of things. Bad Fuel pressure regulator or a leaky injector. Other than that you are just going to have to pull the injectors and and see if they are leaking. Most likely the fuel pressure regulator comes to mind!

bad compression

Reply #10 – October 14, 2013, 10:39:53 PM

oh yeah sorry its the 2.3 turbo with a garret turbo believe its a .60 oe injectors their the brown ones think their like 30lbs boost control nob adjustable fpr aftermarket bov cone filter 2.5in magnaflow exhaust everything else is stock and its putting alot of fuel in the oil in a short amount of time which is why i think the fpr needs adjusted unless the other two injectors i didnt replace our bad or both

bad compression

Reply #11 – October 14, 2013, 10:40:15 PM

Yes, I agree with running the codes. That should at least indicated A problem...I dunno if it will show a fuel pressure problem other than showing the engine is extremely rich through an O2 sensor code...which it must be (extremely rich) if there's fuel in the oil. Just checking the pressure with the vacuum to the regulator should indicate that.

bad compression

Reply #12 – October 14, 2013, 10:43:12 PM

Sorry...I've become accustomed to V8s with the wrong injectors for their tune. The ECM sees a rich condition immediately but can't properly adjust the injector duty cycle to get the air/fuel ratios it wants to see.

bad compression

Reply #13 – October 14, 2013, 10:47:39 PM

id do an engine cylinder balance test and know if it was an injectior problem before replacing anything.

bad compression

Reply #14 – October 16, 2013, 11:38:14 PM

i did the cylinder balance test the injectors are ok i then pulled the vacspooge line off the adjustable fpr and it smelled like fuel im going to test the fuel pressure and if needed adjust the fpr