My Fc is running quite rich. It floods itself out some how...while im driving and just dies. I go to crank and it just won't fire back up. For the first few tries the motor actual starts and immediately dies. Then after about 3 tries the motor quits almost starting and just cranks. Then I will have to leave it for about 3-4 hours or longer. I checked and the car has Spark (at the coils) it has air so it must be too much fuel? Maybe the excess fuel is fouling my plugs? Then the excess fuel evaporates.. and enables it to start?

BTW the gas tank is new, the fuel pump is new as are all filters. The cars motor is rebuilt and has lots of compression. 87 S4 13B N/A Streetport.

Once the vehicle gets running it drives fine and has no problems as long as I keep the rpms up to burn the excess fuel?
Theory number 2. Since the car has the air pump mod to open up the 5/6th auxillary ports , these are set up to come on at 4200 rpms. I rarely get up to that rpm often just right to 4000. So maybe the motor is getting too much fuel because the stock system is designed to go off back pressure so no matter what the rpm as long as their is enough pressure the ports let the additional air in to mix with the extra fuel? and since i rarely go over 4000 then fuel is just building up.. and eventually flooding?


So how can I lean the mixture out some so I can prevent this?

 

you most likely have leaky injectors.

 

send your injectors out. and get the racing beat split pipe thing adaptor. it goes between the motors fuel lines and the ones coming from the tank or by fuel filter. it looks like a capitale H. the bridge allows fuel to return quicker when u shut down the motor

 

The "split pipe thing" is just a bandaid for other problems with the car. A fresh set of cleaned injectors and a car in good tune won't flood.

 

have a fuel pressure test done to see if it's leaking injectors before you start band-aid fixing them, or go through the trouble of having them cleaned.

If the pressure holds after the power to the pump is turned off, then Your injectors are NOT leaking, and your next test would be a compression test, if your engine is has alot of miles and the compression is low it will have the tendency too flood.

Diagnoses is the key here gentelmen.

 

okay well I will check on the leaky injectors and see how that goes. I sometimes smell fuel especially when the AC is on? Is this a symptom? the motor is Rebuilt with low miles

 

If you don't take it over 4K RPM often then you will have to rebuild your engine sooner than you want. You NEED to take it to redline for the engine to blow carbon build up out. Your problem sounds like leaky injectors though. Send them to Witchhunter and get them cleaned.

 

so i have been driving my car the past few days with no problems. I have been driving it kinda rev happy. I managed to make it not start yesterday by driving it for a bit and turning off and on and 3rd restart it failed to start and i had to wait 30 minutes for it to start. I pulled some of the plug wires and they are making spark. Is there some sort of sensor that controls the injectors or would prevent it from starting?

 

Fuel for STARTING is as described in the attachment. The AFM is not used for fuel during starting. Its dependent on the water temperature...rpms....and the ECU seeing the Start signal from when you put the key to Start.

Your problem might be low compression.....bad injectors (primary injectors) or some other item that's lower on my list.

I've found the if the ECU does not see the start signal when you put the key to start, then the ECU uses the afm for start fuel and that amount is MUCH smaller than the internal start map of the ECU. But this only works good it the engines water temp is already fully warmed up. With a cold engine there won't be enough fuel for starting and it will be very difficult is cold weather if the start signal isn't seen by the ECU.

The start signal comes to the ECU on pin 3B, a blue/black wire I believe is the color. Extract that wire from the plug with a hot engine and the thing should start every time when the engine is hot in my humble opinion.

Thats the kinda fix that'll get you thru til you decide to either fix the car or sell it. ECU pinouts are shown in the FUEL AND EMISSIONS section of the series four FSM in the section called CONTROL UNIT.

 

Thank you hailers, I will try to find the ECU and do this when I get a chance.
From FAQ (below)
Do I need to upgrade my fuel injectors in my NA?
Most likely, no. The stock NA fuel system can support up to about 250HP, which you will not be anywhere near unless you are running a big bridge port or a peripheral port. The stock NA actually runs quite rich, so you will see some gains by leaning out the mixture quite a bit. Adding larger injectors is just going to cost you power and waste gas.

If you can gain power from leaning it out.. what is the best way to do this?

 

buy a fuel computer.

You cannot do it with a stock ECU.

 

engines won't stall out due to a rich condition unless it is virtually dumping a stream of raw gas into the intake so i would probably rule that out.

generally speaking, it sounds like low compression since it starts and runs fine when cold but not when hot. your idle is probably too low and when the car tries to idle down the vacuum drops too much and it stalls. you can turn up the idle some to stabilize it but it's just a bandaid to the real problem. do a compression test.

i do see alot of people point to faulty injectors but to be honest, after working on hundreds of 7's i have NEVER seen a single one with injectors that were so bad that they were dumping that much fuel.

 

sorry i didnt describe my problem better. The compression is fine. It just got it rebuilt and only has 70,000 original miles. It was rebuilt because of bad trouble shooting.. not because it needed it. The car starts fine hot. It is something with fuel for sure. I will just continue to drive it. Thank you for answering my question about how to lean out the fuel.

 

I can attest to this happening, on my old 91 NA. The injector was stuck open.

 

I had your exact same problem on a fresh rebuilt N/A.
I shipped my injectors as core and got back rebuilt ones.

Problem solved !!!

As a Bonus, my mileage increased from 17 to 19 in mixed city/hwy driving.

 

Thank you guys ,I will have my injectors cleaned.

 

Just as a sidenote but an important one, I think, Sometimes, regular injector cleaning procedures can't clean all the varnish and gunk that acumulates in injectors, specially those in rotarys, that normally see a tougher environment than a piston engine one (ie. higher temperatures). Also, if the injector is stuck open (one of mine was), cleaning won't help. Finally, if you consider that it is recomended to replace the pinttle caps (plastic covers at the end of the injector), o-rings, and injector gromets (round rubber seal between injector and engine), the price of sending yours as core and getting rebuilt ones that include all those parts as well, is not a bad one. I got mine through RockAuto.com. Got $10 core on each and spent like $140 including expedite shipping.

It is as important to have fully clean injectors, as it is to have perfect ignition system performance in a rotary.

They are great engines as long as they are meticulously mantained.

Good luck.

Kenneth