Fuel Pressure reading

HGN CRVZ · 07-19-2005, 04:53 PM

I have read various posts and found the proper readings for the fuel pressure, but not the indications the gauge just indicate. My 87 when hot, is starting hard and stalling. I checked the fuel pressure and found the pressure at key on to be 45#, but when I start it the pressure becomes severely erratic. It jumps between 47 and 15 almost like a burnt intake valve does on a vacuum gauge.

I originally had a code 36 from the ECM. I conducted the flow chart tests and found nothing wrong with those ckt’s and the code has since disappeared.
Any help would be much appreciated!

Mo_Bandy · 07-20-2005, 02:47 AM

Are you sure your MAF sensor isn't going bad?

The maf will effect the injectors which would effect the fuel pressure...

Hard starting and stalling and erratic "running" is all the symptoms of a bad MAF sensor...

You can easily try unplugging it and see if things smoothen out, it relys on the MAP when the MAF is unplugged , if things smoothen out, the MAF is your problem...

hope this helps..

Mo

Morley · 07-20-2005, 03:52 AM

Quote:

Originally Posted by Mo_Bandy

\
You can easily try unplugging it and see if things smoothen out, it relys on the MAP when the MAF is unplugged ,
Mo

HUH? There is no MAP sensor for a backup on the OBD I systems. If you unplug the MAF sensor the ECM uses default fueling tables based on TPS and CTS readings.

Mo_Bandy · 07-21-2005, 02:10 AM

Morley,

Opps you're right ... I was thinking of my 95 which was anOBD! it did have a MAP as a backup...

Thanks

Mo

HGN CRVZ · 07-21-2005, 10:27 AM

I re-checked everything and found the vacuum hose to the regulator was dry rotted and leaking like a sive and giving the system 20 minutes to sit, the injectors leaked down. I also tried unplugging the MAF and letting the ECM run it's default table for the MAF but the motor died instantly and wouldn't crank until I plugged it back in. I'll have to dig deeper on the MAF problem, but I will try cleaning the injectors and solve that problem first. I had the injectors cleaned by GM two years ago and I just started hearing the injectors ticking again. I think I will also change the fuel filter for the sake of it.

Thanks again for the help!

Dan