Mechanical Fuel Pumps on those big engines!

[Iryanu]

Let's see 'em people!

I've seen a few zombie threads but not a blanket carpet bombing of engine bays with mechanical fuel pumps. I'll get the ball rolling with these, from some unknown dudes:





I'm currently plumbing the engine in my car with a mechanical pump, the holley hp125 is going up for sale, aside from being complete overkill for my modest engine it's a heavy piece and with the re-wire job I'm observing the K.I.S.S rule "keep it simple, stupid". The line lock also went in to the for sale pile, used it once, did a number 11, good times but who has time for that. It's a street car! I can do without the extra wiring and switches and hassle. Stock pump is more than up to the job of feeding my 44IDFS.

Got a malpassi reg and filter going in the engine bay, it's going to be a complete hose fest in there if I don't get some ideas, it seems I'll be doubling back, up to the firewall, then in to a t-piece, not great but I'll try find a way of making it look half way sanitary.

And now for a sermon from Berg:

We are continually asked, "What fuel pump should I use?" Naturally, there are many answers here in relationship to the vehicle weight, gearing, engine, its applications, and power output. As you can see, it is important to be dealing with people that know what you are using and what you need. Be clear this Technical Tip is to make you aware of this area and serves the people that are using our products and combinations (verification required) so we know what to recommend.
Almost all engines will use the stock VW mechanical pump. We ran the stock pump on our 1725 pound race car until it was running in the low 12's. This was possible in part because of the float bowl volume of the 48 IDA, our ball needle and seats and the short amount of time at full throttle opening. Street wise, it is rare that anything but the stock pump will be required unless long continuous speed runs are made or your car is capable of running in the mid 12's. Off-road and other types of racing will depend on power being used and for how long it is being sustained. Should you decide to go to an electric fuel pump, it is critical not to replace it with a unit that is less effective than the factory set-up. This is a common problem for people to make by installing an inexpensive, lesser volume output pump compared to what is removed.
The factory pump, when properly set up, is more than adequate for most applications, which is what lets some people get by with these lesser quality electric pumps. Where we continually see a problem is when at least factory volume is required and the new electric pump cannot supply even the stock volume. People have an overheating or a lean condition, spend forever and maybe even a couple of engine failures because they think they have the fuel problem handled, but do not. They knew they had an electric pump so it couldn't have been that, so they continued to have failures and looked elsewhere. If they get away with an inadequate electric pump, the engine was likely not even using the factory mechanical pump to its potential in the first place.

Thanks peeps.

And yes, the irony of removing one complication and adding another one in the form of a million miles of fuel hose is not lost on me. 

Ryan

[Jeff68]

I have the mechanical pump on my 2110 with IDA's....Because I would like to have my fuel system be able to handle alcohol in the pump gas I have to use (it's all they sell near me) I'm thinking of changing over to Braided lines (Teflon inside) and Aeromotive pump, regulator, and filters. Aeromotive's fuel system parts are compatible with alcohol. I don't think The stock rubber lines and diaphragm in the mechanical pump are compatible with the alcohol in the fuel so it concerns me. Also, I have made "long high speed runs" and did empty the carb. bowls.

[glenn]

2180, 42x37.5, FK8, 48 IDAs, Bosch 010 and mechanical fuel pump



For 99.9% of the time the mechanical pump is fine. The one time i reached it's limit was on an open stretch of interstate, from a dead stop and shifting at 6800 rpm I threw 5th and the engine went lean so I backed off, gave it a second and then put my foot back into it.

It went lean at 105mph.

[cassa]

2.1 liter with mechanical fuel pump. Not exactly K.I.S.S , but seems to do the job 

[glenn]

2.1 liter with mechanical fuel pump. Not exactly K.I.S.S , but seems to do the job 

D'oh, technically .... yes. But not sure that's what the OP was looking for

[Iryanu]

 

Cheers guys. As an update, I plumbed mine all in on the weekend. I'm not really happy with the t-piece arrangement, it worries me! I'm looking at getting a separate fuel block to do the splitting instead of having it hanging out in the wind there. Unless anyone has any suggestions. I'll not be insulted, having the fuel set-up wrong up this end could well... end in tears!

Still got to p-clip the hose to the right hand carb.



That turbo engine.... 

[glenn]

Your generator needs to be rotated 90* CW.

I used stainless hardline with a stainless Tee.

[neil68]

That's my 2332 cc in the second picture of this thread. Ran stock fuel lines up to the engine bay and 12.8 seconds in the 1/4-mile with IDA's.

[RhoadsVW]

2332, 48 IDF's

[Iryanu]

Your generator needs to be rotated 90* CW.

I used stainless hardline with a stainless Tee.

Oh dear on the genny, wont hurt it running it that way will it been like that since 2004 or so? Both cooling slots are exposed.... It's always been that way due to the length of the charging wires in my old loom, I should have known before re-wiring it all! I've gone and chopped the wires there! LOL. Luckily it's on it's own service loop separate from the main wiring so I can make up some new ones and rotate the genny if needed. Bugger it. 

Great looking stainless lines there. Very neat job! 

I'm contemplating getting the 85mm regulator filter which comes with threaded unions on the outlet side, no t-piece needed then, can just use two outlets or one outlet with a "T" on it to go left and right. I'll suck it and see as it is for the moment and come back to it when the engine inevitably gets pulled again.

[Iryanu]

That's my 2332 cc in the second picture of this thread. Ran stock fuel lines up to the engine bay and 12.8 seconds in the 1/4-mile with IDA's.

No regulator? Or did you check with a guage and shim the pump for the correct psi?

[Andy]

This is my 2110 pb et is 13.9 , mechanical pump, no pressure regulator, I just shortened the pushrod until the fuel pressure was correct.

[Iryanu]

This is my 2110 pb et is 13.9 , mechanical pump, no pressure regulator, I just shortened the pushrod until the fuel pressure was correct.

Interesting, see I would have thought shortening it would have an adverse affect on flow, sure it would reduce the pressure, but only because the flow has been reduced. One of the reasons I wanted to have a proper regulator and have the pump putting out what it is supposed to. The numbers speak for themselves mind. Having only run a 15, I could have gone the rod shortening route! Bugger again! Beautiful looking engine bay by the way.  

[Andy]

Thanks,

I don't know the engineering calculations behind pressure vs flow but I know that crossing the finish line in third gear at around 100mph I am not brave enough to look at my afr gauge 

I've never noticed any symptoms of running out of fuel at high speed though.

[neil68]

That's my 2332 cc in the second picture of this thread. Ran stock fuel lines up to the engine bay and 12.8 seconds in the 1/4-mile with IDA's.

No regulator? Or did you check with a guage and shim the pump for the correct psi?

Same fuel pump in use as engine morphed form 1776 cc to 2017 cc to 2332 cc. No regulator and it always seemed to run fine.

[Iryanu]

Apparently the factory pump spec is 2.8 psi @ 3400rpm.

So fine for webers, no need for a reg. Which then makes me wonder why some people have reports of 7-8psi from their pumps? Ah well, looks like I just wasted £50 on that filter king! Triple buggerations.

[Bruce]

It is variations in the manufacture of the aftermarket crappy pumps that cause too much pressure.

About 10 years ago I put together a car with a stock pump.  2275, 42x37 Street Elims, 9:1, FK-8, 48s.  It ran high 12s first day at the track.  When I first put the stock pump on, it generated 11psi!  It took a lot of gaskets to get it down to the right pressure.

[Sarge]

Over 100,000 miles on the current stock fuel pump with no issues... the only issues I've ever had with fuel pumps was with electric models.
As Bruce mentioned above, take the time to set the fuel pressure with gaskets rather then grinding on the push rod.