Air in Mechanical Fuel injection System

Doing a little brainstorming on this issue. Is it possible the low pressure pump is on its way out? I.e. if the low pressure pump is not putting out enough capacity, the main fuel pump could be sucking the FI tank dry after a fairly short period of time. When you let the pumps come up to pressure when you start it, the low pressure pump has enough capacity to partially fill the FI tank. But when you run the engine the low pressure pump can not keep up with demand. Have you checked the low capacity pump to see if it is functioning like it should?

Cheers Jim

 

I'll check on Monday for the Bosch part #. There are only a couple that will maintain flow/pressure and they aren't cheap, I think they are Porsche Turbo maybe. Certainly would suspect your high pressure as I believe in "if things don't change, they must stay as they were", therfore something occured while sitting. Also where and what filters are used, is there a fuel cell with foam?

 

Jim,
Do you spend any time visiting Brian's shop?

George

 

Good luck with it - when I saw this title come back up to the top, I was hoping you had it fixed and were going to tell us the answer.

I for one am totally baffled how air (or whatever, fuel vapor?) could get into the high pressure part of the system unless it came in through the vacuum side of the low pressure system...but I guess that's just me.

Be sure and let us know what happened!

 

That test setup is just "Rube Goldberg" enough to be the work of a real genius.

 

Been following this with interest. I think the suggestion that the feeder pump can't keep the accumulator tank up to level is a great one to investigate.
Otherwise we need to bear in mind that in a pressurized system, the ingress of air is rather difficult.
Could it be that the primary mechanical pump has too much pressure, and thus thepressure difference over the secundary pump is too little?

For an electrical pump, I'd think that even the pump of a Jag EFI V-12 would have enough capacity, and they are plentyful from a junkerif just to try it out.

The test set-up sure looks intrigueing!

 

I mentioned before that on one of my DFVs the injection pump was bypassing way too much due to wear in the shuttle sleeve. After repair the engine ran far better at all rpm's. Glad you have found something. I sent mine to the UK FWIW, around $500 a cople years back.

 

I hated rebuilding the slides! It is absolutely important to follow the original pattern of ball/rollers and total cleanliness, the gas is enough lubrication (another reason to use the 2 cycle oil).

i've redone those a couple of times between practices at GPs, once at the Glen and at Monza.

 

Yes, he has the reputation as the MFI guy. Keep us posted on the progress.

 

Glad to hear this is getting itself back together.

EDIT - didn't mean "itself" - meant glad you guys are getting it back together. Probably at great effort.

 

Looking great!

May we expect some vid of the start-up? Pretty please?

Is that the floor of the new playroom?

 

So glad it's coming back together. It seems that the problem was as on mine, too much clearance in the pump body? these are basically a simple system, but need care to set up and maintain.

Brian

 

That made my Friday. Looks great