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740 No start after head gasket repair (Fuel issue)

S

Supersneak

New member
Joined
Oct 4, 2017
Location
Oregon
So I did a head gasket swap on my 88' 740 Turbo because the engine was running hot. After I got the engine back together and had everything hooked up, the injectors were jetting fuel into the cylinders and fouling the plugs, replaced Ecu. The car would idle, real rough, but after coming back to it about a week later, the injectors are back to jetting fuel. Like they're not receivng ground pulse from ecu. When I plug in a noid light, the light will stay on the entire time + a few seconds after the ignition is off.

Parts replaced:
Distributor Cap+Rotor
Turbo Rebuild
Relays(Radio suppression,FI)
Fuel pump
Injectors
Spark plugs + Wires
Ecu
Coolant temp sensor
Radiator
Thermostat
 
So injectors are constantly being grounded by the ecu. Are you grounds on the intake manifold clean and tight? How’s the resistor pack spades looking?
 
This seems similar to the other recent thread where the wrong connector was put on the wrong place and it too caused super rich flooding. Or, it could be decayed wiring doing weird things. How is the engine wiring harness?
 
I bet degraded wiring under the intake. Injector control circuit shorted to the ground wiring.
 
It's an 88' 740T, the 3 intake ground have been cleaned and checked, I cleaned the resistor pack to make sure there wasnt any issue with the injectors resistance. The wiring harness doesn't look like it's worn or melted in any spots. I just did a fresh timing job on it to make sure my timing wasn't just way off.
 
dl242gt said:
This seems similar to the other recent thread where the wrong connector was put on the wrong place and it too caused super rich flooding. Or, it could be decayed wiring doing weird things. How is the engine wiring harness?
Click to expand...
Can I get a link to the post? Which connectors we're crossed up in that situation?
 
Sorry I can't find it. But it was something like the idle motor was connected to the cold start valve and vice versa. So it turned on the cold start valve and sprayed fuel constantly flooding the engine.
 
dl242gt said:
Sorry I can't find it. But it was something like the idle motor was connected to the cold start valve and vice versa. So it turned on the cold start valve and sprayed fuel constantly flooding the engine.
Click to expand...

Thinking the 88 740 turbo with LH2.2 doesn't use a cold start valve.
 
Supersneak said:
So I did a head gasket swap on my 88' 740 Turbo because the engine was running hot. After I got the engine back together and had everything hooked up, the injectors were jetting fuel into the cylinders and fouling the plugs, replaced Ecu. The car would idle, real rough, but after coming back to it about a week later, the injectors are back to jetting fuel. Like they're not receivng ground pulse from ecu. When I plug in a noid light, the light will stay on the entire time + a few seconds after the ignition is off.

Parts replaced:
Distributor Cap+Rotor
Turbo Rebuild
Relays(Radio suppression,FI)
Fuel pump
Injectors
Spark plugs + Wires
Ecu
Coolant temp sensor
Radiator
Thermostat
Click to expand...

Have you tried swapping the original coolant temp sensor back in?
 
I was looking at the blue temp sensor on the #3 cylinder, and the knock sensor on the #2. They are both 2pin connectors, any chance i could have gotten them crossed, and thats causing an electrical issue? One of my connectors is blue so i just assumed that went to the blue temp sensor
 
I think you could check he wiring diagrams for the color of the wire going to each circuit. If for some reason they’re the same color, you could do a continuity check to each pin on the ecu connector. That will tell you forsure where each connector goes.
 
So I swapped the knock sensor and the fuel injection temp sensor wires. The excess fuel seems to have gone away. The engine will start, rev to about 3-4k and then die. When the ECU is unplugged the engine will turn over but not start
 
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