Alfa Romeo Forums banner

1 - 15 of 15 Posts

·
Registered
Joined
·
156 Posts
Discussion Starter #1
Greetings all. I've been running into some strange problems w/ my spider. The fuel pressure lamp comes on rather randomly after driving a few miles. It's somewhat intermittent for a few minutes then stays on. The main fuel pump was replaced by the PO prior to my purchase of the car (it looks relatively new so I don't think they were feeding me a line of crap). Also, the in tank fuel pump and sock were replaced. I also just replaced the fuel sender unit and clamped on some good fuel tubing between the in tank pump and the sender tube.

Anyway, the main pump makes gurgling sounds as well. Fuses are good, as are connections at the pump. It sounds like there's some air or something in it. The other weird thing is that when the lamp first starts coming on, easing off the throttle makes the light go out for a second or two.

I'm not gonna drive her until I get this figured out. Do those symptoms sound like a main fuel pump failing?

Thanks guys!
 

·
Registered
Joined
·
9,977 Posts
Hi Eric - There could be several causes for the problem.

1. Failing supply pump or wrong type of fuel pump installed
2. Failing boost pump
3. Cracked hose between the boost pump and outlet pipe of the fuel tank
4. Loose dirty electrical connections/poor ground of the fuel pumps
5. Dirty rear fuel filter (especially if tank is rusty inside)
6. Leaking pressure relief valve in the front fuel filter

Take a picture of the fuel pump and post it for me.

You will get some gurgling when you first turn the key to on, but after 5-10 seconds, that should stop as the system gets pressurized and purged. If you're getting constant gurgling, I would look hard at the in-tank boost pump's connection to the outlet pipe.

Since it's cheap and easy, I'd first replace the rear fuel filter to eliminate that as a possible cause.

Also, in the meantime, go to www.wesingram.com/hp.htm and download the Fuel Supply Diagnostics Guide.
 

·
Registered
Joined
·
156 Posts
Discussion Starter #3
Hi John, how's it going?

1. Failing supply pump or wrong type of fuel pump installed

The fuel pressure problems just started a couple days ago so that leads me to believe that it is indeed the right pump (maybe it failed though).

2. Failing boost pump
It sounds alright though (as in a nice constant hum from it when it's on).

3. Cracked hose between the boost pump and outlet pipe of the fuel tank
Replaced that yesterday when I changed the sender. I used 7/16 fuel line & 2 hose clamps so it's nice & tight. I also made sure that the hose clamps weren't touching any of the terminals on the pump itself.

4. Loose dirty electrical connections/poor ground of the fuel pumps
All connections at boost pump are clean and happy. Connections at main fuel pump look good as well, but I'll double check 'em.

5. Dirty rear fuel filter (especially if tank is rusty inside)
Fuel sock looked pretty clean when I had the whole assembly out. The main fuel filter (in engine compartment) is brand new as well.

6. Leaking pressure relief valve in the front fuel filter
I didn't notice any leaks anywhere in the fuel system. But, I'll double check. Is the relief valve that silver thing that's in line after the fuel filter?

Thanks so much! If you ever find yourself in PA I must buy you beer :)
 

·
Registered
Joined
·
309 Posts
Eric;
Has your car been converted to carbs or is it still fuel injected?
I ask because Carbs require a much lower PSI than the FI - my light on the 81 has been coming on, randomly, just within the past week. The only difference is mine never stays on, and I don't hear gurgling. I'm looking for a loose ground wire.
-


If you still have FI, it may be that your pump has failed. You said you hear the hum of the boost pump, can you put your hand on the pump and feel it running while the car is on?
Do you notice any hesitation or engine misfire/poor running?

1. Failing supply pump or wrong type of fuel pump installed
The fuel pressure problems just started a couple days ago so that leads me to believe that it is indeed the right pump (maybe it failed though).
 

·
Registered
Joined
·
156 Posts
Discussion Starter #5
Yeppers, still have the SPICA FI system. I also did an oil change on the SPICA pump when I got it so that end of things should be just fine. It's a matter of getting the fuel to it that seems to be problematic :)

I'll have to grab the pump while running to see what I can feel.

Thanks :)
 

·
Registered
Joined
·
9,977 Posts
There should be a rear fuel filter between the fuel tank and the main supply pump. When was the last time that was changed?

When I say a leaking PRV, I'm talking about an internal leak where the PRV opens prematurely and leaks fuel from the supply side back into the return side, thus lowering the pressure in the supply side.

Does the supply pump emit a nice constant even hum, or does it change pitch?
 

·
Registered
Joined
·
156 Posts
Discussion Starter #7
Supply pump emits a nice even hum. I'm going to do a pressure check on it tomorrow (picked up a gauge today). I'll let you know how that pans out. Also, can the booster pump be pressure tested or is it not a good idea to do a pressure test on that?

Thanks Much!
 

·
Registered
Joined
·
9,977 Posts
The boost pump can be tested. It is permissable to "deadhead" test that one. Looking for 3 - 3 .5 psi

Do NOT deadhead test the supply pump. It can produce high pressure. To test the supply pump, insert a "T" fitting between the front fuel filter and the rear fuel fitting on the injection pump (the pressure side). With the engine off you'll get a nice steady reading. With the engine running, unless the gauge is dampened, you get high frequency swings in the needle due to the individual barrels and plungers in the injection pump filling and pumping. Just try and take an average of the needle movement. Looking for better than 7 psi. Ideally, I like to see 10-15 psi.
 

·
Registered
Joined
·
156 Posts
Discussion Starter #9
Ok, I had my terms reversed in the previous post I guess. The boost pump is what's in the tank, right? I just want to make sure that I'm on your page when it comes to terminology.

Thanks for your patience.
 

·
Registered
Joined
·
9,977 Posts
Ok, I had my terms reversed in the previous post I guess. The boost pump is what's in the tank, right? I just want to make sure that I'm on your page when it comes to terminology.

Thanks for your patience.
Yes, Boost Pump is in the tank. Supply Pump is in the right rear wheel area.
 

·
Registered
Joined
·
156 Posts
Discussion Starter #11
Update: tested the boost pump after the initial fuel filter and it's pushing about 3-4 PSI so that seems to be ok. Testing in front of the main fuel filter will take a bit of doing though as I've got the monofarfalla-falafel monstrosity of an intake.

Might it be a safe assumption though, that if the boost pump is putting out 3-4 PSI that the supply pump is toast?
 

·
Registered
Joined
·
156 Posts
Discussion Starter #12
Oh, just to note, I disconnected the power from the supply pump prior to testing boost pressure so it wasn't sitting there gobbling up air :)
 

·
Registered
Joined
·
9,977 Posts
Might it be a safe assumption though, that if the boost pump is putting out 3-4 PSI that the supply pump is toast?
It sure exhibits all the symptoms of a failing supply pump. Does the engine exhibit any symptoms of fuel starvation when the low pressure warning light comes on fairly steady? If not, you might want to check that the low pressure warning light wire isn't grounding out somewhere and giving you a false light. You also may want to drop alfafan61 a PM after he finally found the cause of a persistent and puzzling fuel low pressure light. He found a problem with the fuel pickup on the bottom of the in-tank booster pump.
 

·
Registered
Joined
·
156 Posts
Discussion Starter #14
Well, I think I finally found the problem. The PO didn't have the rear fuel filter suspended and it was laying on the diff housing. Upon further inspection it was dented to hell & back so that might have caused some capacity issues. At any rate, I swallowed my pride and went to Autozone and got fuel filter FF4506, slapped it on there, primed the system by disconnecting the supply pump and letting th boost pump do its thing for a few seconds. Reconnected the supply pump, fired her up and went for a drive. No fuel pressure warnings or anything. Drove her quite hard on some twisty hilly roads after warm up just to see if anything strange would happen. Not a peep outta the fuel pressure light.

The other nice thing with FF4506 is that it's a bit bigger then the filter that was there so I'm thinking a little added capacity can't hurt.

Once again, thanks a bunch Roadtrip. I should probably be more thorough before I post, but you know how it is. As I mentioned earlier, if you ever find yourself in northeastern PA let me know so I can provide you with beer and grilled cow :)

Thanks
 

·
Registered
Joined
·
9,977 Posts
Mmmmmm. Consume mass quantities of fermented barley beverage and charred animal flesh. We shall endeavor to rendezvous at said location at an unspecified time into the future.

France, I am from France.
 

Attachments

1 - 15 of 15 Posts
Top