robertfrank

iTrader: (27)

Hey guys, My 91 L98 is being a fickle a$$ at the moment. For the last few weeks it's had a slight miss during steady cruise that was progressively getting worse. Last night, when trying to start the car it would just crank over. I first tried to listen for the fuel pump to prime and heard nothing. Second I checked the pump relay and it still clicks. I hooked up my Acton pressure gauge and there is NO pressure in the lines during cranking. Just for giggles, how do I send direct power to the pump to test for operation? I'd rather fix the issue and find out exactly whats wrong instead of throw parts at it. Any help would be awesome.

8Mike9

Check this thread:

https://www.thirdgen.org/forums/tech...o-you-put.html

Veaceonee

iTrader: (1)

Is there pressure in the line before cranking? The ECM needs to see positive oil pressure before it clicks on the fuel pump,

Also, one of the best investments, in my opinion, one can make when troubleshooting fuel issues.
Fuel Pressure Gauge

Beats connecting and disconnecting a gauge all the time.

Have it permanently mounted in my car, can't live without it.

robertfrank

iTrader: (27)

As i stated I DO have a pressure gauge and its reading ZERO during cranking. Hence why I posted this thread.

8Mike9

No, that's incorrect.

The oil pressure switch is a backup in case the pump relay fails.

I/e the oil pressure switch provides voltage to the pump in parallel withe the fuel pump relay.

ECM knows nothing about oil pressure, nor monitors it.

robertfrank

iTrader: (27)

Well i checked out that other thread and I have a problem. My ALDL port doesn't have a clip in the G terminal so I can jump the pump AND my fuel pump test port (C8) is not there. Is there another way to do this?

8Mike9

Yes...pull the Fuel Pump relay out.

I think (will confirm in a bit) jump A to E (outside pins) on the connector, one is 12 from fuse, other goes to FP..

Edit:

A to E is correct.
E is 12v, A goes to fuel pump.

robertfrank

iTrader: (27)

ok I guess I can"t jump those two either.....here's my problem with that...




why would I be missing most of these pins?

8Mike9

Because that is not the FP relay...it should be a flat connector (as I recall) with just 5 pins.

Will be up on the firewall, near the brake booster...not sure exactly on an SD car, as mine is MAF.

Edit:

It is possible it is the FP relay connector for a SD car, let me look at the wire colors in my manual

Edit 2:

Pretty sure you have the wrong thing unplugged, as you connector has 6 wires in it.

The FP relay should be just to the right of the brake booster. In front (on mine) of the ESC module.

My colors:
A-looks brown-dirty anyway
B-Blk/white stripe
CGrn/white stripe
D red
E orange

robertfrank

iTrader: (27)

Thats the ALDL port. I thought thats what you meant lol. I'll try to jump the pins of the relay when I get home.

8Mike9

LMBO!

I though it looked familiar, but spent about 5 minutes all around my firewall to find something like that!

robertfrank

iTrader: (27)

Well I tried to jump the A and E ports with a paper clip and still the pump is a no go. So it sounds like a replacement is in order.

8Mike9

Wait, did you verify voltage first?

Ground to E should be 12 v...

robertfrank

iTrader: (27)

Oh it got voltage alright. I accidently tap E to C and got a good zap lol