On 2012-02-29, Pete C. wrote:

Jon Elson wrote:

Ignoramus14054 wrote:

1) Lack of fuel pressure
Possibly the wrong fuel pump. I would expect this TBI needs
something close to 50 PSI at the minimum.
2) Lack of voltage supplied to the TBI.


Maybe not. The computer probably sends short pulse-width
modulated pulses of 12 V to the injectors. If the starter
isn't too noisy, you should be able to hear it clicking
when you crank. You can definitely hear the injectors on
most injection systems (but maybe not with the starter
running).

You can get NOID lights on loan from many auto parts places (with
deposit), and the injectors are usually driven on the low side.

I have a feeling that both items are a manifestation of the same
problem, which is lack of voltage in the fuel subsystem. I think that
both the fuel pump is not getting enough volts (so not enough fuel
pressure), and also, the injectors are not getting enough volts (so
they do not open properly).

Maybe, should be relatively easy to check. Yes, could be a bad
ground. The fuel pump is probably not controlled by much electronics.
There may be a fuel pump cutoff relay, but that usually is on
cars with airbags.

Two sources of power to the fuel pump, one if the fuel pump relay
controlled by the PCM and the second is an oil pressure switch.

But, I'd measure the fuel pump pressure.
Somewhere there ought to be a spec on fuel pump pressure. A
quick test just with a gauge connected to the pump would tell you
whether you are getting 10 PSI (carb pump) or 50 PSI (FI pump).

According to the doc, the old TBI systems are supposed to run 9-13 PSI,
quite a bit less than the later MPFI systems. A FI pressure tester is
about $20 at the auto parts place.

Where do they plug in?


The injectors may be working perfectly, but with no fuel pressure,
the computer is applying short pulses that SHOULD be right at
the higher pressure.

Also, since the pressure regulator made a difference, it may show
that the regulator has a ripped diphragm, crud under the seat or
some other malfunction. Actually, a typical regulator would
set lower pressure without the spring. But, this one might not
be typical.

Jon