fuel delivery advise needed

Peter Coomaraswamy

Peter Coomaraswamy

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Holiday greetings to all! and thank you all for your help over the last couple of years with my little beast.

This is the third or fourth time this has happened to me in that she refuses to start after sitting, and sometimes even after a drive. I disconnected the fuel line exiting the pump and turned her over... no fuel coming out and the pump and filter are new and the line is clear and yes, there is gas in the tank. Since this is prime driving weather in Texas I was thinking of installing an electric fuel pump as I have future plans to convert to a higher performance FI system after dialing in the chassis. If I were to use an aftermarket pump- just until? what would be an appropriate one to purchase and what would be the best set-up, i.e. location, electrical connections, etc. OR might there be another cause of the failure?

As always, thanks for helping!
 
Peter
Mine has an electric lift pump and I also get a lack of fuel when she has been standing, so far I have found many poor joints and perished hoses, but whilst improved she is still not 100% percent.
Where I would start is checking to see if your car sucking air from one of the many joints between the tank and the fuel pump? Or has the pipe, rubber or metal, got any fractures or got crushed?
C
 
I do not know if your car has a fuel pump relay but if you posted your issue on the E24 forum, most would say this is the culprit.

Leslie Wong has a site about restoring his E3 and I think he goes into detail about putting in an electric pump.
 
I use the lift pump assembly from a 633csi to feed my Webers. The assembly is very close in length to the stock sender/pick-up unit, and it puts the pump where it really belongs - in the tank. I have never had any fuel deprivation problems, and the e24 sending unit works very well with the stock Bav gauge. If you are considering changing to FI at a later date, simply add a stock HP pump in the line, like the factory setup.
 
Thanks, I have a 633 parts car, so I'll pull the fuel pump. I'll also test the lines, though all rubber hoses are new I guess there could be some air leaking in. I have heard that some people shave the fiber block where the pump sits on the head- would that be worth trying? It seems like everything should work and it does sometimes, just wants to leave me high and dry every once in a while. Please keep the suggestions coming. And being the lazy boy that I am, are there any circumstances in which an aftermarket in line fuel pump would be applicable as a back up?

Happy Thanksgiving
 
Peter Coomaraswamy said:
Thanks, I have a 633 parts car, so I'll pull the fuel pump. I'll also test the lines, though all rubber hoses are new I guess there could be some air leaking in. I have heard that some people shave the fiber block where the pump sits on the head- would that be worth trying? It seems like everything should work and it does sometimes, just wants to leave me high and dry every once in a while. Please keep the suggestions coming. And being the lazy boy that I am, are there any circumstances in which an aftermarket in line fuel pump would be applicable as a back up?

Happy Thanksgiving
Click to expand...

While replacing the hard line that runs from the front of the car to the tank, I found that it had several sections that had been "repaired" by splicing in rubber hose. You might check to see if you have the same as I doubt they can be all that effective for long.

Also, I'm not sure if it's a '74-only thing, but I had two hard lines running front to back. If you do, you might try using the other to see if that helps.
 
The rubber lines at the tank and at firewall to the pump can bleed air and look perfectly fine but it allows fuel to return to the tank. They crack with age and create the symptoms you describe.
 
Peter Coomaraswamy said:
are there any circumstances in which an aftermarket in line fuel pump would be applicable as a back up?
Click to expand...

I would not put an electric pump in series with your mechanical pump. If the diaphragm ruptures you run the risk of introducing fuel into your crankcase, seldom a good idea.
 
Have you considered a circuit like a csi where the fuel pump in the tank is energized by the wire that operates the starter? Using a 1991 318i fuel sending unit with its two 8mm fuel lines and the low pressure pump from the 633 csi you would have a combination of mechanical and electric ( only for priming ).
I will be in Austin next week if you want me to bring you one.
 
question

sorry to poke in, but sfdon, if you set up circuit as you describe, does that pump work continuously (prior to ignition), or is there a pressure sensor somewhere that tells it to stop when pressure is sufficient?
 
Only works when the engine is cranking.
Ljet is set up this way.
Switch in AFM turns on fuel pump when engine is running.
Fuel pump runs when AFM door is shut but starter motor is cranking.
The easy primer system.
Black yellow to starter twins off to pin 85 of the fuel relay allowing fuel pump to run when cranking or running.
 
Fuel supply mystery

Hello,
I have seen many references to the carburetor Coupes not wanting to start after sitting. Looks like we all suspect fuel pump, change it, and change rubber sections of the gas line, make tight connections, and still no fuel coming out other side of pump. I am wondering if the fuel tank sender has any role in this. Just how does it work inside? I have replaced my pump with a new one, (then have doubts about what "issue" Peirburg I may have bought) still no go, then tried a known working original, no go. Then I read of the sleeve around the first 3 cm or so on tank sender pipe that may crack and allow air in. Yes, it was cracked, took it off and used 2 hose clamps to be sure no air. No difference. have ordered new rubber o-ring for tank sender, though the original did not look crushed or flat, but perhaps a source of air getting in. Any other thoughts out there?
Thanks for any tips.
Mike
 
Well, here is something to check. Does your gas cap suck in when removing? Sometimes the one way venting of the cap stops working creating a vacuum in the tank restricting gas flow.
 
If you pull the sender unit you can check the screen for debris. Your fuel filter is new I presume.

How long does it take before it finally starts?

bluecoupe30! said:
Hello,
I have seen many references to the carburetor Coupes not wanting to start after sitting. Looks like we all suspect fuel pump, change it, and change rubber sections of the gas line, make tight connections, and still no fuel coming out other side of pump. I am wondering if the fuel tank sender has any role in this. Just how does it work inside? I have replaced my pump with a new one, (then have doubts about what "issue" Peirburg I may have bought) still no go, then tried a known working original, no go. Then I read of the sleeve around the first 3 cm or so on tank sender pipe that may crack and allow air in. Yes, it was cracked, took it off and used 2 hose clamps to be sure no air. No difference. have ordered new rubber o-ring for tank sender, though the original did not look crushed or flat, but perhaps a source of air getting in. Any other thoughts out there?
Thanks for any tips.
Mike
Click to expand...
 
Fuel supply mystery

Great ideas. Yes fuel filter new. In fact I was trying a clear one for this diagnosis to see if fuel got in. Never thought about gas cap, or the venting of the tank. I will investigate. Takes several cranks to near start, then starts. Or at least used to. Got to get this moving...it's blocking my Healey! Will report any progress. Thanks for some direction.
 
Fuel Supply Mystery Solved.

So, I replaced the fuel sender o-ring, nice and snug, got a new fuel tank cap, and still no fuel coming out of pump. Finally disassembled Peirburg and noticed no movement when I worked the pivot lever, so I took off the gasket and worked it and packed it with grease and worked the lever again. Seemed to be a much more effective operation. Also, as I had the sender out to replace the o-ring, I saw the fuel level was near the bottom of the tank. The guage read 1/2 full. Hmmm. So I opted to put a few more litres into the tank, charge the battery and try again.
Took many cranks but, behold, it started! I think it was a combination of a few things : air possibly getting in around sender o-ring, low fuel level ( now I have to research what's up with my guage), old, not well sealed rubber hoses, and that Pierburg that seems to want to seize up if let to sit for a while. I hope the generous greasing will help. Thanks to all of your suggestions. I had a great drive today!
 
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