She's a drinker.....81SC

Jim Savage · 11-29-2004, 01:06 PM

Help!

Finally got the 81 Sc motor (original CSI) fired and running. But man does it suck the gas. Went through a couple gallons in a couple of minutes of idleing. But the idle was high at 2200 rpm. AAR?? WUR??? What should I look for and how do I test it???

Help?

Jim

anthony · 11-29-2004, 01:15 PM

A gallon per minute seems impossible. I'd figure out where the gas is going. If it's going into the oil you could ruin the main bearings.

widebody911 · widebody911's Garage

So this is a Top Fuel dragster then?

Jim Savage · 11-29-2004, 02:28 PM

I couldn't believe the fuel sucking either. But it does drink heavily. I had temporarily hooked up a 2.5 gallon can to the pump. (long story). I ran that tank dry in 2-3 minutes of the car running at a high idle. Thought I was crazy.....Filled the can again and same thing. I thought maybe some valve was stuck somewhere and forcing the idle to be high. Didn't know if anyone had heard of this?

Will check the oil tank level tonight...Hadn't thought of that.

Jim

David Goodman · 11-29-2004, 02:45 PM

Jim,
My (rudimentary) understanding of CIS is that more fuel that can be used is sent to the system and then returned to the tank unused. Just a guess, but you may find much of the missing fuel in the tank. It sounds like you only rigged up the supply (not the return) to the can.
Dave

Jim Savage · 11-29-2004, 02:46 PM

Duh.......I feel stupid.....Wasn't thinking clearly. Was so excited about getting the engine running that I didn't think about my test tank setup.

I disconnected the suction line from the tank and put a temporary line into a 2.5 gallon tank (was eliminating suspected bad gas as problem of not running). But I didn't take the return line off going back to the normal tank. So all my "extra pressure gas" was returning to the big tank and not my 2.5 gallon tank. Duh........

See, there are stupid questions on this board.

Now if I could figure out the high idle, I'd be one happy dude. Maybe it's normal and I didn't let it warm up enough.

Jim

Jim Savage · 11-29-2004, 02:48 PM

Thanx Dave. That was it........

Jim

David Goodman · 11-29-2004, 02:52 PM

Sounds like you figured it out for yourself. It was just a matter of time. Not a stupid question at all, you just had to take a step back and think about it.

notfarnow · 11-29-2004, 02:57 PM

Just curious, why does the system draw more fuel than it can use? Is there another reason for this, maybe cooling fuel system components?

white87911 · white87911's Garage

Just curious, why does the system draw more fuel than it can use? Is there another reason for this, maybe cooling fuel system components?

My answers to the above question

keeps fuel cool,
less drawl on the fuel pump, due to less pressure against it,
no drop in pressure when fuel demand suddenly spikes.

notfarnow · 11-29-2004, 03:10 PM

Quote:

Originally posted by white87911
keeps fuel cool,
less drawl on the fuel pump, due to less pressure against it,
no drop in pressure when fuel demand suddenly spikes.

Thanks, that makes perfect sense

Jim Savage · 11-29-2004, 03:24 PM

Yeah....its been engrained into my head. "One fuel line from the tank to the pump"....Can you say Chevy, Ford, American made.

I have learned to think "outside the box" working on the 914 and 911.......

Thanx for the inputs from this board!!!!!

Jim

Paulporsche · 11-30-2004, 06:35 AM

Jim,

Your idle speed may simply be set too high. Adjust the large screw on the side of the throttle body. Your WUR or AAR could also be out of spec. You may be running too lean, possibly from an air leak. Your fuel dist plunger could be stuck. Your timing could be off. Lots of stuff to check. Try the speed adjustment first, and then check your mixture.

speeder · speeder's Garage

If you can run it long enough to get it warmed up, you can at least attempt to adjust the idle the normal way. (Air screw). Could the distributor have gotten turned (advanced) somehow? Do you have the Bentley manual for the car? Good luck, and let us know.

Jim Savage · 11-30-2004, 08:41 AM

Well first things first. I started this test to prove (or disprove) if I had bad gas (no jokes). It is bad.

Since it runs on known good gas I am in the process of draining the tank and filling with new. While I'm in there, going to change the two hoses under the tank.

After this is done, I will
1. Warm it to running temp
2. Check timing (doesn't look like it has ever been adjusted)
3. Check for vacuum leaks (I suspect this is it)
4. Check throttle body idle screw
4. Check WUR
5. Check AAR
6. Check Plunger

Hopefully it will turn up somewhere in that process.

No Bentley, but Haynes and this board has helped tremendously.
This has been a long and ongoing project of installing this 81 SC into a 76 911. I'm excited about getting it this far.

Thanx for all the input.

Jim