MSefi.com read only forum (Jan.15,2018)

After finally getting my truck to start, and not fall back into the "cranking" parameters, I have a small problem. I am sure there is a simple answer.

After deducing that the engine really was running out of fuel, and not losing spark, I pulled the fuel line off the TBI and put it in a clear water bottle.

Flicked MS on - got a good, strong prime
Started cranking - steady, strong stream of fuel, just like the priming pulse, only continuous
After cranking for a few seconds... - the fuel pump started spitting out little shots of fuel, good pressure, but the duration of each squirt was very short

There is no way that the little squirts of fuel the pump is supplying to the TBI are enough to build up and sustain sufficient pressure for the injector.

If I was an MS guru, I would know immediately which parameter(s) to "add to", but I am clearly not

What should I fiddle with to get constant, and good fuel?

As a side question. Let's say I set it to always have as much fuel as when I start cranking, the fuel that isn't used will simply run back to tank right? I only, really know diesel, this is why I am having so much trouble...

WELDER

do you have a return line from the pressure regulator back to the tank ?? It should be one big loop from the tank to the filter, to the pump, to the injectors, to the regulator, back to the tank.
what you describe sounds like a single line system with air. Fuel should be constantly flowing when the pump is on (and it should be on for 2 seconds after powering up the MS, then during crank and run).

LEs

Well there is my problem

I have a stand-alone fuel pressure regulator, but I don't have it currently installed, as I was told that GM TBI's have a built-in FPR.

My system is as follows:

Tank>pump>filter>TBI>tank

When I get home, I will try to "bleed" the system, although I doubt it will do anythng, since it seemed like the pump was actually being switched off.

The other option, is to put a simple rocker switch and fuse in the pump's positive wire and run it the cab.

Thanks for the confirmation Leslie

Yes, GM TBIs have a built-in FPR, it’s the small cup that hangs down between the 2 fuel line connections. They are factory set about 12-13 psi (except for late 454 units set at 30 psi).

After deducing that the engine really was running out of fuel, and not losing spark, I pulled the fuel line off the TBI and put it in a clear water bottle.

Which fuel line did you run to the bottle, the feed line or the return line? Regardless, either one should give a steady stream if the engine isn’t running. If the return line pulses the FPR could possibly be resonating/pulsing open-closed, but if it’s the feed line you have a problem with your pump, suction filter, wiring to the pump, etc.

Thanks Fury.

I used the pressurized (to-TBI) fuel line for my little test.

I will go wire the pump to a rocker switch, see how far I get tonight, then report back here.

Thanks for the help so far.

Welder

Well, it looks as though my pump is what's FUBAR.

12v supply > switch > fuse> pump > ground

The pump acted the same way as previously described.

I shall spend money, thus fixing the problem

Thanks for the help guys (girls if any).

Welder