EFIDynoTuning Forum

Well... just after the Y flange the exhaust system had been stolen. Essentially, there is no exhaust system.

I am curious about the vacuum under starting conditions. If good vacuum isnt achieved, maybe that is evidence of incorrect valve timing.

I still suspect the injection issue is computer related, and not input related.

Would erroneous MAF or Cam data stop injector pulses?

I have not used starter fluid, next time i'll try that.

These are the digits on the PCM.
XC3F-CFD
MCM3

Now, in fairness, those codes are on the black box which houses the PCM. I have not removed the PCM to verify what codes it has on it.

Where is the MAF sensor located? On the port side of the engine, over the head, there is a smallish magnesium box with a 4? wire plug going to it, and a what appears to be a vacuum hose. I figured that was the MAP sensor.

I've tried starting without the cam sensor, crank sensor, and MAP sensor. Engine response is the same.

What i cant understand, is after a start attempt, reset to run, and start again, i wait for fuel pressure to build back to 40psig, and no pulses.

I'm thinking the PCM has failed, or i'm wondering if there is something in its code where it will only command 5 injections if a condition isn't met. Might there be a transmission sensor that if malfunctioning, triggers a "no injection" response from the PCM?

Are there timing marks on the balancer and cam sprockets to verify valve timing? I googled and couldnt find an anwer.

The old man's daughter sold me the motorhome, the service was years ago, as was the overheating incident. He told her "engines blown"...

A crack head cousin and her friend lived in it for a year... then they stole it... then the daughter got it from Dad to fix up. They're cutting their losses. This is all of the info i have.

I bypassed the fuel pump bc its check valve has failed, and to make sure i had full pressure.

Fan is mechanical, not electric.

Engine will not start.

Previous owner claims after recent service he was driving and noticed the engine was overheating. Pulls over, coolant everywhere. Parks vehicle, comes back later and it will not start.

Removed and replaced all fuel.
Replaced fuel filter.
Good compression. Good fuel pressure.
Checked most COPS, all good.
IACV is open.
No damage to wiring or connectors found.
Verfied spark while cranking.
Bypassed fuel pump relay (always on)

Now here is the weird part. Pulled the starboard fuel rail, left injectors attached. (Unplugged COPS)

Turn key to on, then start. 5 pulses from the injectors, and fuel pressure drops from high 30's to mid 20's.

Injectors stop pulsing.

Let off start (key resets to run) and try to start again. No pulses. Try again, no pulses.

Turn key off and on, "start" again. 5 pulses then nothing. Reset to run, start, and nothing.

Engine does not fire at all, even with the 5 pulses.

Ohmed crank and cam sensors ~330ohms each. New sensor is 350ohms.

Inertia switch isnt tripped, not sure if that matters. Did not verify intertia switch continuity.

Lastly, tried to pull codes with Scan Gauge II, despite 'Service Engine Soon' light being on, no codes were present.