MFI Fuel prob uphill?
 

So after an issue I had with my fuel pump last year on a DDK club run I've been doing major surgery on the fuel system in my '72.

Here's what's changed:

New fuel pump
Tank filter replaced
All fuel hoses replaced
MSD + Blaster coil + clewett wires + new plugs

Coming back home after a 40 mile trouble-free run today there's a long steep hill. I was following slow traffic, dropped back a bit to get a good run at speed up the hill. Towards the top I started to get all the signs of fuel starvation, engine just dying. I had to stop, and the car would restart but run extremely badly, barely idling, and usually quit. I rolled back down the hill and got it on the level. Another few tries to get it running again and I had it idling badly again, I held the fuel linkage at full throttle and as if a blockage just cleared the engine roared into life, and ran fine after that.

A few hours later I had another run at the hill (car runs fine otherwise) and had the same symptoms, this time there was no traffic and I just kept my foot in and cleared the hill. The trouble went away on the way down. I then drove 30 miles back home on the highway with no problems. Gave it full throttle at an offramp and the car pulled like a train :confused:

Perhaps some moisture could have gotten into the fuel system? A blockage in the tank at the pickup? I guess the other thing I haven't changed is the fuel filter as that probably had less than 2000 miles on it although probably 5 years old.

How good was the rebuild on the fuel pump? Since they are not available new, any "new" pump would be an aftermarket part. If that is the case, did you make sure the specs are correct: large volume, high pressure.

The pump is new, one of the ones from fuelpumpking1 on ebay. Check the early S tech board, theres a thread about them on there. Some discussion that they might be for a Volvo application but look very similar to MFI ones.

It seems to deliver fuel fine in WOT, high rpm situations other than this hill incident so am reluctant to blame it.

Long time ago I had this problem with my 70T. Fuel starvation going up hill. Finally discovered a piece of metal had come loose inside the tank. When going uphill it would roll down & block the pickup. If it happens again try stopping, roll backwards & turn around so you're going downhill. Roll down the hill aways then hit the brakes hard. If it immediately clears up then that could be you're problem.

Good Luck

I had a similar problem in a TR-6 once. Dirt in the fuel line would settle in a bend on long uphills and restrict the flow enough that the car wouldn't run. I've also heard of issues with the fuelpumpking MFI pumps.

Thanks guys, maybe I'll have to pull the tank and give it a clean. :(

Update on this, had the car out today and managed to reproduce the problem.

Its not related to hills, so its not crap in the tank, but rather using sustained full power. All signs point to inadequate fuel pressure.

I was overtaking a small van and mid-way through the manuevure the car started to miss, just as before, and eventually got so bad I had to pull over. I finally got the car running again by cranking multiple times with full throttle, this must get the pressure back up in the mechanical pump and eventually it was back to normal.

I think we need to issue a caution on these newer Bosch pumps until we can be really sure they are ok :(

Unfortunately, I have one of the fuelpumpking units. I haven't tried it yet because the car isn't together. I'm going to be upset if I wasted all that money, but at the time I couldn't find any alternatives and was worried about finding _anything_ usable.

I saw this recently:

Zims Replacement Fuel Pump for 911 69-73 w/MFI

Anyone have experience with them?

Check out this thread.

http://forums.pelicanparts.com/porsche-911-technical-forum/163347-mfi-fuel-starvation-out-ideas-help-please.html

If you get two fuel lines mixed up the car will start and run but starve under load. There were some incorrect fuel diagrams that were reprinted over the years.

Check it out!