Fuel Pump Suggestions or Sender

[drcomanche]

So, I've been trying to diagnose why my truck is running rich and I have come down to the fuel pump and whatnot. Now, when I replaced the gas tank, I got a good look at it, and it was a jerry rigged set up to say the least. The pump itself was held on by metal clamps to keep it from moving with a large chunk of metal to space it correctly. So, what do you guys suggest. I'm not sure if it's just the pump being poorly sized, or if my sender is broken, but what would the likelyhood of this being my problem be?

[alleydog]

I don't think the fuel pump will make it run rich, Have you checked the fuel pressure? Does it start ok cold or hot? Try pulling the vacuum hose off at the fuel pressure regulator. If there is gas in the vac. line, your fuel pressure regulator is leaking.

[drcomanche]

I actually just replaced the regulator. I'm not sure about the fuel pressure, don't have the tools to read that, but it starts fine, hot or cold with no problem.

[flint54]

Curious how rich it's running. Black smoke? Badly fouled plugs? Sudden large unexplainable

drop in mileage? I can't imagine a fuel pump causing too rich. Fuel pressure gauges aren't

very expensive, and really helpful to help diagnose. Three factors control fuel rate: 1) the

orifice size (doesn't suddenly change), 2) the ECM input to the injector coils (pulse time), and

3) the fuel pressure. If your fuel pressure measures nominal (which I think is around 32 psi

with vacuum connected to the reg and 40 psi with vacuum removed from the reg) I would

suggest pulling injectors and have them flow tested to see if perhaps one or more are leaky.

If pressure checks out, and the injectors check out, the only thing left is what the ECM is telling

the injectors to do, and why. My recent "too rich" problem was due to unstable vacuum to

the MAP sensor, which in turn caused the ECM to do crazy things. I've had O2 sensors go TU

and cause similar issue. (sometimes I really miss the old points distributors and the dual carbs).

[drcomanche]

You know, I had completely forgotten that, of all the things I replaced, I never managed to get my o2 sensor out to replace it. That thing is practically cemented into the exhaust pipe. I'm pretty sure it's never been replaced, either, so I'll go try to yank that out.