Fuel pump problem?

[Jayru]

Ok guys, picked up my 72 240 today and already started working on it. The Good; has the round top SU's on it (built before 9/72 i guess), and the Single point distributor (prime pertronix conversion).

The bad; Won't start. Checked ignition that's good. Fuel looks real filthy in the fuel filter, but no gum/gunk in the lines. Sprayed starter fluid in the intakes and she fired up one crank! But then she dies. It's running on the starter fluid only.

Here's my question:

I stuck the feed hose in a tank of clean gas with a new filter. If you look at the clear filter it looks like the gas is barely being sucked in by the Fuel pump. You literally see it trickling into the filter. I have no experience with mechanical F pumps, is this normal or is my pump bad?

I would think the filter would be full of fuel and you wouldn't see any air in there to even see it tricke in.

Let me know what you think.

Thanks,

Jay

[Bambikiller240]

You will see some air in the filter. Has the car sat without running for a long time?

How long did you try to start the car with the alternate fuel supply?

Remember these pumps only generate a few lbs of pressure, not like an EFI fuel pump. It can take a bit of time for the fuel to fill the lines and float bowls of the carbs.

See http://www.classiczcars.com/forums/showthread.php?t=15474&page=1&pp=15 for an example of what other people find in cases similar to what you describe.

[Jayru]

Nothing like that thread, the lines are clean and ungunked. Besides, it won't start with the new fuel supply line in the gas can. We let it run for about 2 minutes on the starter fluid with the new line/gas can, and still wouldn't stay running.

Fuel literally trickles out of the filter inlet like a faucet that is almost shut off. Could their be a problem with both carbs not letting fuel get into the jets? That wouldn't explain the trickling fuel filter though.

It sat for about 6 months, but he started and ran it occasionally.

[Bambikiller240]

Fuel filter is BEFORE the fuel pump, you won't see pressure there. (unless you have a electric fuel pump near the tank)

How are you sure the lines are clean? Have you looked into each end of the lines? in Engine compartment, and back by the tank? Blown air through them?

If everything is as clean as you say, it can only be a couple of things. Pump or Carbs.

Wait, you say it ran with the alternate fuel supply for 2 minutes? What was forcing the fuel into the carbs? The pump? If so, then it almost has to be lines plugged as you've proved the fuel pump and carbs work.

[MikeW]

Fuel literally trickles out of the filter inlet like a faucet that is almost shut off. Could their be a problem with both carbs not letting fuel get into the jets? That wouldn't explain the trickling fuel filter though.

Normally the filter would be between the fuel tank and the mechanical fuel pump. You might consider running the output fuel hose from the pump back to the fuel can just to see how much it really pumps when you turn the engine over a few times. You could even remove the pump (just three 3 screws) and operate it by hand.

[Jayru]

Fuel filter is BEFORE the fuel pump, you won't see pressure there. (unless you have a electric fuel pump near the tank)

Wait, you say it ran with the alternate fuel supply for 2 minutes? What was forcing the fuel into the carbs? The pump? If so, then it almost has to be lines plugged as you've proved the fuel pump and carbs work.

No, no, you misundersood my post. It ran for 2 minnutes because we kept spraying starter fluid in the carbs. We did this to give the new line/filter time to fill up with fuel.

and it still Didn't run. I don't mean to say pressure at the filter either. I would think there'd be enough suction at the filter to fill the entire filter so you wouldn't see it trickle in.

Sorry if i wasn't clear.

[Jayru]

Normally the filter would be between the fuel tank and the mechanical fuel pump. You might consider running the output fuel hose from the pump back to the fuel can just to see how much it really pumps when you turn the engine over a few times. You could even remove the pump (just three 3 screws) and operate it by hand.

We tried to mimic the pump action by hand with a spare pump, the previous owner gave me, and the new fill hose/gas can. But the car wouldn't run then either. I don't think we can possibly pump it fast enough to keep the car running, but we couldn't tell if the new pump was pushing fuel any faster than the old one.

The pump doesn't look easy to change. their is some weird giant iorn bracket surrounding it with ~7 bolts holding it to the block and front cover. Otherwise i would have just changed it already. I guess i'll just remove the bracket and pump tomorrow and see what happens.

[Bambikiller240]

Yes, I misunderstood what you were saying. If it ran on the starter fluid, then carbs should be relatively OK

I haven't looked hard enough to see a "trickle" of fuel into my fuel filter, but there is always visable "air" in my filter. (and my car runs just fine).

You might try what MikeW said about routing the output of the pump into a container. If that doesn't confirm a bad pump, my bet is still on plugged lines or fuel tank pickup tube. This is an extremely common situation when a 240Z has sat for a long time (even if started once in a great while). Fuel turns to jelly and rust in the tank combines with it to plug things up.

Inlet and Outlet Hoses and 2 nuts and one bolt should be the only things to remove in order to change the pump. Do you have a picture to post of the bracket you're referring to?

[Jayru]

I'll try and take one tomorrow. It surounds the entire pump from all 3 sides, only the top of the pump is visible. It ataches to the block on the side and the t chain cover from the front.

thanks for the help,

Jay

[beandip]

You might still have the filters at the inlets to the carbs, where the fuel line attaches. Check there and remove them and leave them out.

[MikeW]

The bracket in question is for a dealer-installed A/C compressor. My car had exactly the same setup originally and I just happened to keep the unit after removing it years ago. The compressor itself is a Borg-Warner unit. I just put it on a scale and it weighs a whopping 32.5 pounds.

When I first bought my car one of the first repair jobs was replacing the fuel pump and I remember how that bracket was in the way. It's been so long that I can't remember if I had to remove it or could somehow get the fuel pump out while the A/C bracket was still in place.

[Jayru]

That's the one, although the compressor is gone. It doesn't appear the car ever had A/C lines in it though. Weird.

I'm going to look for those filters at the carbs and change the FP today if i have time.