CIS fuel pump with carbs?

[al lkosmal]

I've heard that using the CIS fuel pump with carbs is OK. If so, what regulator is being used???

TIA

Al

[RoninLB]

There are two designs of fuel regulators used in our cars depending on the fuel pump application.

A CIS pump with a return line would use a back psi regulator. The back psi regulator is like a relief valve dumping excess psi into the return line. In design the carb feed is before the valve. The relief valve allows high flow rates without over psi the pump. It's actually a more efficent design than the routine pressure/dead head regulator.

The most popular model around here is the PMO that's sold by Pelican. It's a very nice "plug and play" unit.

[al lkosmal]

Ronin,
Thanks. I will check it out.

[RoninLB]

Don't remember who's car.

[al lkosmal]

Ronin,
That looks nice. It appears that the setup there is fuel-in to the fuel block w/gauge and then out to the carbs with no return. At least not one that's apparent in th pic. That's what I am doing now, using a facet fuel pump and holley regulator and pressure gauge. I haven't heard great things regarding the lifespan of the facet, so i was thinking of returning to my CIS pump. I'm wondering if I can simply switch back to my CIS pump and use the existing plumbing.

[RoninLB]

Originally posted by al lkosmal
and then out to the carbs with no return. At least not one that's apparent in th pic.

, using a facet fuel pump and holley regulator and pressure gauge.

i was thinking of returning to my CIS pump. I'm wondering if I can simply switch back to my CIS pump and use the existing plumbing.

the return is there

this is the Holley you're using? If so then that regulator is a pressure reduction unit. You can't use it with a CIS pump.


The PMO regulator is about $75.

That said there are options on how you design your plumbing. All it takes is $.

If you decide to use the CIS pump the 1st thing I would do is install the CIS pump. Then connect the discharge in the engine compartment directly to the return line with ONLY a fuel psi gauge to measure the line back pressure. If your line pressure is over 3.5psi you'll need a more complicated design. The lower the better.

[al lkosmal]

That's the one. thanks for the info. I'll check into the PMO regulator.

[RoninLB]

Originally posted by al lkosmal


no return.

just to add pics to this thread. While fooling around I wound up with an extra strange pic that I'll post anyway.

I couldn't find a regulator pic while searching the PMO site. If anyone knows who recently posted this pic on another thread please post the info because I want to send an installed pic to PMO.

[al lkosmal]

Ronin,
That PMO regulator appears to be on the fuel inlet side of the pressure gauge. I remember this thread and the fuel inlet is thru the regulator, gauge, to the two banks of carbs vis filters and then the two banks of carbs were tied together at the back end. Kind of a fuel loop, "to help equalize pressure", but with no fuel return. i like th nice, simple regulator.

Al

[al lkosmal]

Or is that the inlet sneaking in at the bottom side of the fuel block?

[RoninLB]

I gave away mine for free as I wanted a Mallory back pressure reguator so I can't give hard info on this one's hook up.

The pressure on this regulator design is measured before the valve as the regulator discharge is blown off or dumped as a pressure relief valve would blow off on your home hot water heater. The carbs are thus fed from a T like design at the set pressure before the regulator. Lets say the PMO has two Ts. Each T is dead headed. There is no loop through both carbs.

I tried the full loop plumbing. It didn't work for me as I had too much back pressure/friction in my return line. I had 5# back pressure without the regulator. When the regulator was installed for testing the back pressure increased 1# . When I replace the return line with a better line my friction will decrease and I'll be able to do a full loop. That's why I said above to measure your back pressure by connecting the pump discharge in the engine compartment directly to the return line with only using an accurate psi gauge and run the regulator full open or don't install the regulator for testing. Keep the carb lines disconnected for ease of testing. Many of those 15# gauges are not accurate. Confirm your gauge somehow.

The full loop is the best. If you do a full loop use a different back pressure/ return style regulator like the Mallory I'm using now.

You have options on your plumbing one way or another. I hope my bs is clear. I'm no prize on explainations..

meanwhile I have pics of the Mallory if needed ?

[buster73]

On my PMO weber conversion they used a simple pinch clamp in the return line to adjust the fuel pressure in the supply circuit. Never had any issues with it.

[deanp]

I used the PMO regulator and fuel bars with my set up. There is a return line on there, you can barely make out the fitting behind the fuel supply line tothe carb on the left. I have a filter in-line before the regulator.

[RoninLB]

Originally posted by deanp

There is a return line on there, you can barely make out the fitting behind the fuel supply line tothe carb on the left.

I have a filter in-line before the regulator.

hey Dean

That's eyeball candy you have there. It's beautiful imo.

I sent you a PM w/my e-mail asking for a big bit pic so I could crop it and present the regulator area only. You don't have pelican e-mail forwarding.

And you confirmed that the regulator input is that line on the left side of the regulator that's pronounced?

And it looks like you used 45 or 30degree couplings? That's a plumbers dream as it has less friction, technically and actually, that a 90deg.

What kind or fuel filter and its micron filtering size did you install ?

" That said there are options on how you design your plumbing. All it takes is $. "

[RoninLB]

Originally posted by buster73

used a simple pinch clamp in the return line to adjust the fuel pressure [

hey Guenter

They work nice and pinching the hose is commonly used. Yours looks better that the routine hose clamps that I've seen. You could do a full loop around the carbs with a pinch clamp if wanted. No worry about a regulator diaphram leaking fuel with your install.

Looking good imo.

What brand of fuel hose are you using ?
What manufacturer clamp are you using ?

[buster73]

Originally posted by RoninLB

What brand of fuel hose are you using ?
What manufacturer clamp are you using ?

I'm just in the process to reinstall all new fuel lines. Using black 7 mm braided rubber lines (as available from our host). The clamp does not show any manufacturer markings, but as I was told it was part of a PMO conversion kit.

[RoninLB]

Thanks G

I was playing with "paint" and was able to label Dean's pic.

I don't think any more pics are needed?

[Porsche_911s]

If anyone knows who recently posted this pic on another thread please post the info because I want to send an installed pic to PMO.

jwetering posted those pics on a thread I started. Some of the pics were early in the install and he later posted some once it was done.

[Porsche_911s]

If he uses the PMO regulator, how does he hook it up to the CIS lines? What is the adaptor to make the lines fit? I'd also like to know; I went with a different fuel pump but would like to use the CIS lines but I have not found anyone local who has a fitting that will mate with one of the CIS lines.

Ronin,

I did some searching and found how you did yours. It'll probably be easier to just stop by a shop and have a new end put on the CIS hose.

[RoninLB]

Originally posted by Porsche_911s

how does he hook it up to the CIS lines?

I did some searching and found how you did yours.

ok.. so you know what to do now ?
The shop should/may have the correct dies for the factory connector. Not all shops have them. They fit the ss 6AN perfectly.

thx for the site where I got the pic from.