Fuel Head

[JFairman]

yeah were having some fun now...



I almost lost this little valve and spring in the control pressure circuit. I didn't know it was in the top half of the fuel head under the threaded stainless steel plug.

The bottom half of the fuel head was still outside soaking in lacquer thinner when I took these pics.

[boosted79]

Very timely thread, I'll be doing my '79 shortly plus the WUR and making it adjustable. They look like pretty good kits.

[heliolps2]

good luck sir...

[JFairman]

cool.
Your '79 came with a cast iron fuel head painted black. It has a stainless steel diaphram instead of a rubber one and no lambda circuit fittings.
Tomorrow I'll try putting it back together...

[Rawknees'Turbo]

So the diaphragm is FUBARed by ethanol, just like you predicted (not all that old either, right?). And the one in the kit is supposed to be resistant to it, correct?

The kit looks good - what are your first impressions of the quality, Jim? Did you buy the assembly guide pins, too (or maybe you plan to make some yourself)?

[JFairman]

The kit description says the diaphragm and o-rings are ethanol tolerant. This is a CIS Flowtech modified fuel head I bought around '07. Ran perfect for about 9 years and then something went wrong in the fuel head on number 4. I can't see any tiny holes in the diaphragm but I havn't looked real hard at it yet. The 3 big 0-rings that fit around the control plunger cylinder look a little funky. Uninstalling the cylinder with no oil on them is tough on them so it's hard to say from looking at them.
It's getting new ones and I'll put a little motor oil or WD 40 on them while reinstalling everything so they hopefully slide down into place and don't tear. It's a tight fit.

[MikeD930]

Man...I'm glad my 930 does not have CIS. I can't stand ethonal...it messes up my other tools/toys (lawnmower, chainsaw and dirt bikes).

So you decided to keep your 930?

[xbmwguy]

I'm glad I don't have that "outdated crap" either.as far as ethanol 85% or none

[boosted79]

They are pretty simple, no big deal. Just have to make sure to get the pressure set correctly and each of the injector ports flowing equally.

[JFairman]

I wouldn't call them simple.. compared to EFI of any type they are extremely complicated as far as the amount of mechanical parts involved that have to work together correctly.
Last night I was holding a small flashlight up to the different ports and passageways in the upper and lower fuel head chambers and then looked for traces of light in other ports and passageways. These things are complicated, especiallty the bottom half. I have a basic understanding but I don't know everything about them.

I will do flow tests again into small plastic bottles with and without injectors on the ends of the injector lines.
They were balanced well before when you held the sensor plate down around an inch so they were spraying a lot of fuel. Probably similar to when at full throttle and full boost but at idle #4 was spraying too much fuel and it kept spraying a little fuel with the motor turned off and the fuel pumps on. The rest of the injectors would shut off completely then.
I moved injectors around to different injector lines and #4 kept spraying if the pumps were on and the motor was off so that tells me it was the fuel head.

Here's a pic of the fuel levels in the plastic bottles after an injector flow test a few weeks ago while the sensor plate was held down around an inch. The injectors were all spraying and screaming in a big way during this.
The motor ran smooth on all 6 cylinders above 2000 rpms but below 2000 rpms it would run on 5 cylinders or something like 5.5 cylinders whatever.


#2 and #5 sprayed a little more fuel than the others and I think thats just right because #2 and #5 probably run a little hotter than the others. The exhaust ports and header tubes for #2 and #5 always have a lighter color carbon in them than the others.

I also did the same injector flow test with the sensor plate pushed down about a millimeter so they were just starting to spray. Takes a while but then #4 would fill up a lot faster than the others.

edit: I didn't buy the $80 stainless steel assembly guide pins. The 1 3/8" long Torx bolts that hold the top and bottom halfs together seem like they will hold the diaphragm in place while snugging down the bolts so it doesn't seem like you need them. They would be nice though.. Just have to make sure all the little spring seats, springs, and white plastic discs are in the right places and don't move out of place while assembling it.

I wonder what kind of plastic those little white discs are made of. They are what get pressed up against the orifices above them to adjust and control fuel flow and volume to the individual injector lines by turning the little 3mm allen head screws under the 4mm button head screws. Turn them to the right to increase spring tension and push the white disc and diaphram downwards away from the orifice for more fuel injected (richer mixture) or to the left to reduce spring tension so the disc is closer to the orifice for less fuel (leaner mixture).

I just hope this thing works after all this... Or I'll have to send it out and spend over $500 with shipping two ways to have it rebuilt.

[boosted79]

These are simple compared to a Bosch VE diesel injection pump. I've had those apart and it still amazes me how they work. I'm sure you'll be able to get yours working fine. The injectors add another variable into setting the flows, I wonder if the flow test could be done without the injectors?

[JFairman]

I check them without the injectors on the lines first just to see what I get and then again with them on the lines.
The injector pintles don't pop open until they see something like 30 or 35 psi so I think final adjustments should be with the injectors on the lines.

[boosted79]

How did the flows compare w/o the injectors? I agree, the final test has to be with the injectors. Did you clean the injectors by holding the pintles open with a piece of wire and soaking them?

[JFairman]

Originally Posted by boosted79

How did the flows compare w/o the injectors? I agree, the final test has to be with the injectors. Did you clean the injectors by holding the pintles open with a piece of wire and soaking them?

It was about the same.
Yes, I wired the pintles open again and soaked them in Techron and then with Break Free which is made for cleaning gun powder residue carbon out of barrels and actions of firearms. I clamp the injectors inside a small bench vice while wiring the pintles open.
Then I put them in a small Harbor Freight ultrasonic cleaner filled with Break Free for around 10 minutes.

Then I put a 4" long piece of 8mm fuel hose over the pintle end of the injector, filled the hose with puff can carburator cleaner, and blasted the carb cleaner through the injector in reverse with 120 psi air pressure from my compressor to try and rinse any possible dirt off the little fine screen fuel filter inside the injectors. I use a small hospital grade needle nose hemostat to carefully grab the pintle and pull it open a hair while wrapping a single strand of copper wire around it. Then fold the ends of the copper wire over the sides of the injectors so you can slide the 8mm fuel line on over them.

Very important: Hold the ends of the copper wire tight against the sides of the injector while pulling the 8mm fuel line off when you're done or the fuel line might pull the pintle open too far and possibly tweak the small internal spring that holds it closed. If that happened the opening pressure of the injectors may become lower and the injector might leak and drip fuel after shutting off the motor until the residual system pressure being held by the accumulator and multiple system pressure check valves drops down to nothing.
Leaking injectors is a common problem with old CIS injectors that become dirty with carbon under the injector pintle seats. The reason CIS injector pintle seats slowly get dirty from carbon is because they stay open continuously while the motor is running.

EFI injector pintles are constantly opening and closing while the motor is running and that helps keep them clean. They are self cleaning in that way. The dwell time or amount of time EFI injector pintles stay open combined with the system fuel pressure is what changes EFI fuel volume and pressure, and the air fuel ratio.

[boosted79]

Great info, thanks. I ordered my Salvox rebuild kits this morning.

[Jeff NJ]

I think I just found a winter project... great stuff Jim. Keep us posted on how it turns out.

[timc]

Originally Posted by boosted79

They are pretty simple, no big deal. Just have to make sure to get the pressure set correctly and each of the injector ports flowing equally.

Yeah, I to made the dumb statement years ago that CIS was dead simple, and that was just based on my limited experience of rebuilding a WUR and setting fuel and control pressures based on temp and O2 readings. After following some of Jim's threads, and talking more with my brother, this stuff is anything but.

FWIW, nice thread....

tim

[boosted79]

OK. What may be complex to some may be simple to others.

[T77911S]

this may be too late.

you really need(ed) to check fuel flow with the sensor plate pushed down or held down with something that could be consistent for repeating the test for a certain amount of time.

I made a shim that fit under that bar that goes across the top of the AFM and held the sensor plate down. (actually made 3 different ones).

to set the fuel head back up to the way it was its not just balancing the cylinders, its setting the amount of overall flow,.
say for an inch opening of the plate for 1 minute it could be set to flow say 10oz of fuel or 15oz of fuel.

I have seen other pics of that fabric and they all looked like yours


your fuel balance looks pretty good. I don't know if you could get it any closer.
when you put it back together set the balance initially with it open about an inch. then go back and check it like it would be open for idle. you want this to be closest for the best idle.
put a battery charger on the battery and run the pump for about 30 minutes to get a good check. the longer the better,
then make a last balance check at WOT just to verify it.

oil on the Orings helps a LOT when going back together.

I would inspect the surface of the plastic valve seats for any defects or flatness.

I am not a fan of propping open the pintle. I did that on 2 of mine then decided to have the tested. 2 injectors blew the pintles out while being tested. not sure if it was because of what I did.

[JFairman]

This is a CIS Flowtech modified fuel head so I'm not changing overall flow, I'm trying to fix it so all the ports flow equally at idle and a little above idle speed.
Over 2000 rpms it ran smooth before.

The upper chamber port that flowed the least out of all 6 had it's 3mm spring tension adjuster turned clockwise all the way so the diaphram was pushed down as far away as possible from the upper chamber metering orifice that leads up to the injector line for that port. The other five 3mm allen head spring tension adjusters were not screwed down all the way, they were all adjusted to flow close to the same amount.

If the thing doesn't work right after all this I don't know what I'll do. Maybe start saving up for EFI and sell the CIS. I like EFI and I've disliked CIS ever since the first time I saw it around 1980.

I like high compression fast responding normally aspirated engines best. I hate delayed reaction turbo lag and waiting for the limits of ancient CIS to respond to throttle position changes during acceleration just makes it worse.