My 1982 XJ6 S3 starts then stalls. It appears to be fuel related. Both tanks removed and cleaned. new fuel pump fitted. new filter fitted. Ran fine on left tank. fitted new return valve to RH tank. not starting on RH tank
Water in fuel. switched to LH tank. not starting. Drained fuel from lh tank, disconnected RH return valve. Car starts runs for 20 seconds or so then cuts out no fuel. Fitted another new fuel pump, replaced Fuel filter
fuel pump gets noisy as if straining to deliver fuel. replaced coil. replaced spark plugs set throttle plate to .002" checked all vacuum pipes, repaired leak at flexible pipe between AFM and throttle intake.
As soon as i pump fuel pressure up with turning the key to start position while in gear car will start and run well for 20-30 seconds then cut out.
Any suggestions?

 

Hmmm.

Here's where I would begin:

Remove the fuel pump relay so you can jumper the terminals in the relay socket. You want to apply 12v to the white/green wire (or wires) ..... so jumper the white wire to the white/green. This bypasses the control circuit; the pump run whenever the key is 'on'. Now start the engine and see if anything changes. If the engine now stays running we can dig into repairing the control circuit.

A loud fuel pump is a little worrisome. New pumps are easily injured by debris in the gas. It might be overheating and stopping. But, try the bypass first to eliminate a problem with the control circuit.

Cheers
DD

 

I have bridged the relay, car does start and run. Idles for a minute then starts to stall. If i"m quick on the throttle it revs up. Fuel hoses have been replaced, the old ones were hard but open.
I have tried 2 other computer boxes. The large hose from the MAF to the intake split when it backfired, I have temporarily repaired with duct tape. All vacuum hoses checked.
Vacuum hose to brake booster checked. Booster operates correctly.

 

Sounds like fuel starvation. After checking wiring connections then you must still have a reduced flow somewhere. Some put and extra filter between tank and fuel pump to stop rust/debris blocking it. Had same problem which was solved when wiring connections cleaned and pump and filter changed (twice).

 

I have fitted 2 new pumps and filters 2 months apart, replaced fuel hoses. Old hoses were hard but open. It runs fine at 1200-2000 rpm. Drops to 1000 when accelerator left drops to500-600 rpm then cuts out.
I bent an aqllen key to fit 5the idle screw. But the screw is very tight, i don't want to force it. I will of the MAF and the unit to clean it.

 

The fuel filter is in line after the fuel pump so more than likely you have a blockage on the inlet side of the pump. There are both rubber hoses and metal pipes between the tank and the pump so even if the tanks were cleaned there could still be a problem.

 

I have used the pump to drain fuel from the tank, Fitted a pipe to output of pump plenty of flow. Pump runs quietly. replaced all flexible fuel hoses from pump forwards
Bridging the relay keeps the car running if i hold the revs at 1500-2000. let go the accelerator revs drop to 1000 rpm . When it drops to idle 600rpm it cuts out.

 

I can feel your frustration, lets try this: Bridge the relay and turn the key to "start" with your foot off the gas pedal-does it start? If yes, does it idle cleanly for a few seconds and then die? If you are quick on the throttle and bring the RPM up to 1500+ (example), will it run for as long as you have the throttle at that position? If yes, begin to lower the throttle very slowly and note how the engine is running. For example: 1500rpm-engine is running smoothly; 1400-same; 1300-same; 1200-just a slight change; 1100-same; 1000-slightly rougher sounding; 900-rougher still; 800-same; 700-very rough running; 600-rougher still and then it dies. Another example: 1500rpm-engine is running smoothly; 1400-700rpm the engine is still running smoothly; 600-engine dies like you had just turn the key off.

The first example would tell me there is a fuel or air problem, the second example would tell me the problem is electrical. Back to the beginning, can you start the engine and run the same tests with the fuel pump relay in place? If no, I think I would start by trouble-shooting and fixing that issue first. After that, we can concentrate on mechanical/fuel trouble-shooting. Unfortunately, my "lump" doesn't use any of the same fuel-related electrical pieces of a stock S3 and I don't have first hand knowledge of their operation, but there are others here that are far better versed in that area. I would recommend that you download a copy of S57 electrical diagrams for your car, an absolute must in my opinion. You can download for free here: https://jagupgrades.webstarts.com/

Dave

 

Sounds like the bellows between throttle body and air flow meter are bad, not enough air moving past the blade in the meter to open it and make the pump run, with relay back in place, if you manually open the flap can you hear the pump running?? Key on engine off…

 

Thank you for all the good advice. I replace the clamps holding the pipe between the AFM and the inlet manifold. (The clamps were not tightening properly)
Now running great. There was a pinhole just behind the clamp. The new clamp is wider and covers the hole. I am sourcing a replacement pipe. Currently starts when i turn the key from outside the car.
Going to take a long test drive today