In-Tank Booster Pump Replacement

**alfafan61** · #1 (**permalink**) 09-12-2007, 01:09 PM

This is a tale of sound and fury. Mostly mine. The problem started when I was bringing my Spider back to life after a 10 year rest.

It had been converted to carbs and I was converting back to Spica. Once everything was connected I was not getting enough fuel pressure. It was steady but low. I made a mistake and assumed the main pump was failing and replaced it. Only to have the same problem. I then found out about the in-tank booster pump. I pulled the sending unit and found this nasty lacquer encrusted thing that was frozen solid. I cleaned/replaced that as well as the small hose. Now I had much more pressure but it would build up and die repeatedly. So I proceeded to replace both fuel filters again and then replaced every inch of fuel line front to back, checked the PRV at the main filter, and experimented with different size restrictor ports. All with no joy. Then, with no other choice I got another new fuel pump thinking I had a defective one. This did not fix the problem. At about this time with a very angry wife staring at the check book I decided to re-check the booster pump. I had ruled it out earlier as I had a dead-head reading of 3.5 PSI so thought it was fine, and after all it was new.

The installation was fine. The only thing that could be changed would be the black rubber boot that fits on the bottom of the booster pump like the attached crappy drawing.

It has 2 holes in it of different size. Either would fit around the booster pump intake. As I did not closely observe what hole went where at the initial replacement, I assumed the big hole should be placed around the pump intake. I was wrong. Turns out if you place the large hole around the intake you will get fine dead-head readings but the fuel flow will not be enough to keep up with the system requirements causing cavitations and pressure drop-off. Once I re-assembled the sending unit with the small hole around the intake my pressure problem was solved. My guess is that the design of the black boot works with the intake to provide the needed feed for the booster pump. I will need to leave it up to someone on the board versed in Fluid Dynamics to confirm or deny this. In any case it now works, so if you replace the booster pump pay close attention to the black boot and the 2 holes.

Now that the pressure problem is solved I now need to replace the brake master cylinder. I am sure to get nasty looks from the wife.

Any one need a new fuel pump?

alfa_bob · #2 (**permalink**) 10-24-2007, 09:44 PM

This sounds so like what I went through. My problem was after a comlpete strip of the car (1979 Spyder) for a restoration, I could not get consistant gas supply. I did most of what you did before finally finding out that I had not conected the power supply to the booster pump. We learn from our mistakes!

tokky28 · #3 (**permalink**) 02-10-2008, 09:44 AM

I seem to having a similar problem now. I was driving yesterday under relatively warm conditions 80+ and the car starting missing occasionally when I down shifted and floored the gas. It gradually got worse to the point that I was really limping home. The car's got about a third tankful of gas. Could it be that the fuel level got low enough that the main fuel line isn't getting enough fuel without the assistance of the in-tank pump (assuming that the little hose failed)? If that is the case, does the sender/tank gasket need to be replaced when re-installing the in-tank pump?

Thanks,
Andre

**alfafan61** · #4 (**permalink**) 02-10-2008, 11:37 AM

Andre:

Before even going down that path, check your fuel pressure light. If it is on constantly it can be filters, fuse etc, check all of the simple stuff first.

tokky28 · #5 (**permalink**) 02-10-2008, 03:00 PM

It came on intermittently. I've tried resetting the intertia switch and am I'm going for another test drive now. Will report the results.

Thanks,
Andre

**Roadtrip** · #6 (**permalink**) 02-10-2008, 04:53 PM

Do you have a copy of the Fuel Diagnostics Guide that you can download from www.wesingram.com/hp.htm?

tokky28 · #7 (**permalink**) 02-10-2008, 06:50 PM

Hi John,

I did review that. It seems that it may be the inertia switch for now. The last time I took it out before the symptoms showed, I bottomed the car out a couple times over some uneven pavement. I think that may have dislodged the switch some. I tried fiddling (i.e. resetting) the switch and the fuse before the drive this afternoon and woo hoo, it has been good since! Keeping my fingers crossed.

Cheers,
Andre

**Roadtrip** · #8 (**permalink**) 02-11-2008, 12:54 PM

The switch can come apart and be cleaned. There's a previous thread on how to do that.