Compression? Injectors firing?

Need to get a compression tester tomorrow to know for sure. And I'm guessing the injectors are pumping cause I can smell gas. Did notice with throttle wide open while cranking it sounds like it wants to back fire.

had the exact same problem also in a conversion, turned out to be the cam angle sensor was out 180degrees

Update: got compression readings on the cylinders. They are pitiful at 0,45,35,45. Is it possible that the timing may be out 180? And would that cause such a low compression reading?


P.s. I checked the cam sensor too. Thanks for the tip.

I think you meant to say cam angle sensor (CAS) out 180 (since you said "I have double and triple checked my timing") and no, CAS out 180 would not cause low compression. Timing off 180 would however although it probably would bend valves also.

Thats what I thought. But it rotates over by hand normally. I guess my next step is to pull the head and see what's going on in there?

luv2rallye said:

I think you meant to say cam angle sensor (CAS) out 180 (since you said "I have double and triple checked my timing") and no, CAS out 180 would not cause low compression. Timing off 180 would however although it probably would bend valves also.

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my cam angle sensor was out 180 degrees and that 100 percent caused it to crank over and over but not quite start

benny23 said:

my cam angle sensor was out 180 degrees and that 100 percent caused it to crank over and over but not quite start

Click to expand...

That's not what I said. I said it does not cause low compression. I agree CAS out 180 would not allow it to start since injectors and spark would be all wrong. It does not change when valves are open which is one thing that changes compression.

Pulled the head off and inspected the valves. Everything was strait and seated good against the head. Got new head bolts and reinstalled head got everything back in time. And checked compression. All numbers still low dry and wet compression tests.

Its a 420a for those of you saying the cam sensor is 180 out. OP Is it an engine that's been sitting for a long time? If so the rings may be stuck. Try a 1/4 cup of diesel in each cylinder over night. Then put a rag over it with plugs out and pump diesel out. Then retry the comp test. If its still bad, then sounds like the rings are gone. You could check be adding compressed air into the cylinder from an air compressor if you have one. Remove the timing belt and let the cams sit with all valves closed and listen to where the air goes. Intake? Exhaust? Bad valves. Crankcase? dipstick or oil cap. Excessive blow by would be rings.

GOT IT! The dowl pin in the exhaust cam broke. So the sprocket was is time but it was spinning on the camshaft causing the low compression. Got a junk yard cam in there and now she's good to go. Thanks for the help gentlemen.

Wow that's unusual. You're very lucky you didn't bend exhaust valves.