Madeline's 850 cranks but does not start. I unplugged the air mass flow sensor. After about 10 seconds of cranking it produced a massive backfire. Smoke came out all all sorts of places and did loosen the oil filler cap. Impressive.

The fuel pressure regulator vacuum line did smell like fuel, but with a backfire like that, it would not surprise me that fuel vapor was everywhere. Fuel pressure looked good (~44 psi and held 40psi for a couple minutes. 20 psi for quite a while.)

How do I check the camshaft position and crankshaft position sensors ?

Any other ideas ?

Thanks

Greg

Madeline's brother replaced the rear crank shaft seal because it leaked oil? I wonder if oil got into the crankshaft position sensor(CPS). That would really mess things up and give faulty readings.

You need to recheck the CPS after the brother played with it. Just make sure it is clean and the wires do not go anywhere near the plug wires. Too bad they wasted money on a new battery.

Klaus
--
Common sense trumps a PhD

I hope you cleaned up the driver's seat after that one :)

Your oil filler cap could only be loosened by a crankcase explosion, unless it wasn't tight before!

I guess you have spark. Recheck your air intake fitting and any other vacuum elbows. Inspect the vacuum tree for loose items.

I haven't seen any Ohm figures to check the MAF or CPS. If either fail completely, there is a code for that. But erroneous readings from either...

Your fuel pressure should be around 40psi, so I guess the FPR is OK.

Klaus
--
Common sense trumps a PhD

One problem is that Madeline and her brother replaced the battery since it was last running. No codes are stored... It was a big backfire. If this car had a carbuerator, it would have burnt the paint off the hood.


Greg

When you get off work today, pull the plugs and clean them off. Let the system air out for a while. Check the wire that goes from the CPS and make sure it doesn't rest against a plug wire, use a zip tie to keep it away fron the distributer. Keep the MAF unplugged, that should trigger a code. Then try starting it again.

Oh, with the plugs out, check to see if there is spark at #1 by cranking it a bit with the plug grounded somewhere.

Hopefully, the backfire was only in the exhaust manifold and down pipe.

Klaus
--
Common sense trumps a PhD