faxayres

I guess this is going to be the winter I learn to work on my CIS...

Here's what happened, and then I hope some of you CIS magicians will have some idea where I should start (my car is an 83SC with the stock 3L):

At VIR this past weekend, I ran low enough on gas during a session on track to gulp some air - and other bad stuff, I'm afraid - into my fuel system. Two times I think the motor sucked air. Immediately after the second time, the car started running like cr*p. Back firing under load, throttle cutting out and in under load, rough running and backfiring at idle, engine stopping and then hard to start, and everybody who listened to it agreed it sounded like it was running on only a few cylinders.

I let the car idle for about 10 mins, and then took it out in the next session - after adding new gas - and limped around the track for about 4 laps, car burping, backfiring, and running terribly.

At idle, I removed spark plug wires one by one to see what effect that had, and in apparently four of the six cylinders, it had almost none.

I took off the fuel filter and drained it to see what was inside, and I swear it looked like apple cider - dark and full of lots of particles of stuff. No water separating out though, as far as I could see. This filter has less than 8K miles on it, and is about 18 months old. I tried to salvage the filter by filling it backwards with clean gas, sloshing it around, and dumping it out the inlet side - waste of time. I re-installed the filter, started the car with great difficulty, and drove it around the paddock to the horrified stares of everybody I drove by, and then coaxed it onto the trailer and came home.

So...my assumption is that the car sucked some gunk into the fuel system when I ran it too low on gas. And my question is..

What would you do, and where would you start?

dsmith

Well, I can offer up what to check, but I've been unsuccessful all year in fixing my similar drivability issues. I'm down to rebuilding WUR and testing injectors. After that, I give up. Hopefully, solving your issue may help me.

1. Make sure your 02 sensor circuit is working (fuse in trunk, relay under pass seat, frequency valve buzzing/vibrating (feel by hand)). If your interior lights don't work, start here.
2. Check ignition timing, make sure you get full advance at 6k rpm
3. Check fuel pressures. Look for too high system pressure and/or warm control pressure.

I would call CIS the devil, but, since I haven't solved my issue, that would be premature.

David

art

Hopefully the filter caught any particles, so there should not be contamination in the system. Try taking out all injectors and put them in jars, run fuel pump and open air flap wide. This will flow lots more than it does when running and will push some minor crap out of the injectors if it is there.

If the fuel pump ran dry long enough it may have overheated and be sub-optimal now. Do you have a filter between the tank and pump? (do these cars have two pumps?)

If you have that much gunk in your tank it's time to clean it out or replace it. Get a pressure gauge and check pressures in the system, this will point you in the right direction. Gauge is cheaper than any component replacements, so if you only were to guess (which is what you will be doing without it) wrong once, it is paid for.

Peter Zimmermann

Step 1. Remove large section of trunk carpet.
Step 2. Locate fuel gauge sending unit in top of gas tank (near brake booster).
Step 3. Remove sender.
Step 4. With luck the tank is almost empty, so you'll be able to determine its condition, including the pick up screen.
Step 5. Will be based on result of Step 4.

Houpty GT

The tanks are just plain steal on the inside and they rust.
Here are some pics in another thread. https://rennlist.com/forums/showthre...=373752&page=3

As for sucking in gunk when the tank runs low, I do not believe this. I have never seen any proof that this happens and all the people who say it just don't know. The gas is taken from the bottom of the tank all the time. These tanks also have some sort of fuel screen filter housing. I am not sure exactly how it works but I seems like it would probally keep a good deal of gunk out.

The fuel screen can be removed from the bottom of the tank. Use the top side of a 13/16 spark plug socket as a substitue for a 22mm allen wrench. Just pull the rubber plug out that holds the ceramic on the spark plug and slide a 3" extension in there so you can use a ratchet on it.

Don't rule out any normal problems with the cis but think about what could have happened when your pump ran dry. Running lean can cause some serious damage (valves, pistons) but I can't tell you how long it takes to do that.

Check your fuel system and check the compression of your engine.

smakuch

Your fuel tank is full of rust.......as my 83 was several years ago. Shortly after replacing all of the injectors, it would shut down......or run poorly. If it stopped, it would start after a while. Turns out powdered rust passed thru the filter into the injectors & other components & stop the fuel flow. Get the tank cleaned & sealed, & clean out the fuel system. It's been good for me for about 60K miles as daily driver. Garage queens will rust up the tank.
steve

theiceman

there is a small screen ay the wur also. Take the lines off and check this also .

faxayres

ay the wur...?

dsmith

Uh oh, time for some homework! Budget a couple months for some CIS learnin'

http://members.rennlist.com/jimwms/CIS/CIShome.html