V-Fib

Okay, Oh wise ones,
The 79 has been running extremely well, then suddenly.................
Starting running rough, will hardly run at idle
Backfire on decel through exhaust
Running very rich, all plugs extremely sooty/black
Ignition components all check out fine.
Fuel system pressure at 5.7 bar Pump replaced this year
WUR replaced this year
Auxillary air valve-Replaced this year
Thermotime switch replaced this year
Cold Start valve-replaced this year
All injectors replaced this year (I don't think they're the problem anyway)
Fuel Tank, accumulator, filter and fuel lines replaced this year
Infact the only thing in the fuel sustem that hasn't been replaced is the fuel distributor.
I am thinking it is now time to change it out.
Any comments extremely appreciated..........

largecar379

ignition timing? where have you set it?

if it's at factory spec--advance it--really advance it.....

less fuel lingering around after ignition (down firing--not back firing), more responsive throttle

I don't even use a timing light anymore for my final settings, just when first setting up a motor. from there it's run the rpm's up to 3000 and adjust distributor to where the engine speeds goes up the furthest. I'm running nearly 40 degrees advance-all in-no spark knock on crappy 91 octane....

Have you "drilled" your injector lines, cold start injector line, WUR lines?????

Ask Chuck about mine--he drove it at 3rd Coast and remarked how he couldn't believe how quickly the engine revved up......

--Russ

Dennis Wilson

Anthony,

Check the relief valve on the back of the fuel distributor. If the o ring for the pressure release has deteriorated and plugged the return line it would cause too high system pressure and extremely rich running. This happened on my euro. I suspect the high pressure also caused the collateral damage to the other o rings in the distributor.

Dennis

V-Fib

Thanks for the responses. My ignition timing is advanced a little over, but I have had no problems running 93 Octane. The 79 pulls very hard at about 30-35 mph and up, being a 3 speed auto. A 5 speed would be better. The difference between the USA 4.5L and the 80-83 4.7L Euro has to be felt. Dennis, I was leaning strongly toward the fuel distributor as the culprit. I have read the threads of those who have rebuilt it, but will probably just call Jim B. and get started on that 2-3K per year for maintenance for 2008.

Dennis Wilson

Anthony,

Agree that rebuilding the distributor is a hit or miss proposition. If the o rings in the relief valve are going, the other 10 in the distributor aren't far off. If you have a CIS pressure tester, it wouldn't hurt to check it before going for a rebuilt.

Dennis

V-Fib

Thanks Dennis, I do have a tester. I know the System pressure is 5.7 bar, It's a matter of checking control pressure, right?

Dennis Wilson

Anthony,

I don't have the chart handy but did you check to see if the 5.7 bar is within the range? You may also want to check the flow/pressure at the injectors. A simple test would be to pull the injectors (leave the fuel line attached and fuel pump relay jumpered) and check for flow with the air sensor plate closed. There should be little or no flow until the air sensor plate is opened. If there is flow with the plate closed, this normally indicates bad o rings in the distributor which allows fuel to bypass the controlled upper chamber metering slits.

Dennis

Agent_13

My 78 was running a little rough at idle. I started pulling plug wires, and found 2 cylinders were not firing. I knew it had spark, and good injectors, so I pulled the Fuel Distributor. After taking it apart, I can't believe it was running at all. It was completely full of Varnish, and Rust. How any fuel made it past is beyond me. It still ran fairly strong, and smooth. I spent 5 hours cleaning it, and purchased all new O-rings. Its going to be reassembled, and installed tomorrow. I can't wait to see how it runs afterward. I was a little nervous about working on the FD at first, but after taking it apart, and seeing how simple of a device it is, I have no worries at all. You might want to check this on your car as well.

Dennis Wilson

Definitely agree that the fuel distributor is not as complicated as many carbs I've worked on but it is touchy. The toughest past is getting it back together without leaks. The tendacy is to use gasket sealer but too much can plug the small decoupler holes in the gasket. My trick was to clean, clean and reclean with with a razor and solvent on all the mating surfaces. I also used wheel grease rather than sealer on the mating surfaces. The grease may sound funny, but it washes out of the orifices and it seals at the flat surfaces. Telling my age here, but this technique was used on old flat head engines that had stamped steel head gaskets.

Good luck,

Dennis

hupp

System pressure spec for a '79 US is 5.2-5.8 bar. Anthony's system pressure is within spec.

I replaced many of my CIS components as part of a restore with exception of the distributor (4 years ago). My car began to run very rough with no power about a year after the restore. All system/control pressures and fuel delivery rates checked within spec and spark was good, so the last piece of the puzzle was the distributor. I replaced with a rebuilt unit from 928 Intl and man what a difference. My car runs like a top -- cold weather starts, hot weather starts, hot engine starts, warm engine starts - everything is solid.

Might be time for a new fuel distributor.....

V-Fib

Thanks guys, 29 years for a part is great longevity. I am still amazed at these cars, even after 6 years of ownership.

928ntslow

Is there a specific fuel distributor rebuild kit or will a box of various sized O-rings do the trick? I am thinking I need to give mine a refresh as well.

toofer

If you go thru with your plan and still there is little or no improvement run down all the vaccum lines to be sure one hasn`t worked its way off.

Dennis Wilson

No kit that I know of since this is a factory repair item. The correct size o rings should be available locally but make sure they are fuel/petroleum resistant.

Dennis

928ntslow

Well, I had ordered a CIS test kit from JC Whitney and thought they promised shipment on 12/28, they changed it to 1/4...now they changed it to 1/25, so it's gonna be a bit before I can test. No hurt in rebuilding this thing in the interim. Can't hurt huh? Rich A's PDF is a good one and i will head over to the hardware store to track down the necessary O rings. There is a lot of nifty places up here in "stump town" that deal in hydraulics and more. I should be able to find everything I need. Thanks!