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Old 09-18-2018, 07:21 AM   #1
Supersneak
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Default No start after head gasket repair (Fuel issue)

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
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Old 09-18-2018, 08:55 AM   #2
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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?
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Old 09-18-2018, 03:28 PM   #3
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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?
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Old 09-18-2018, 04:40 PM   #4
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FPR will flood the injectors for some reason when they fail they go full pressure ... what year car etc that would help
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Old 09-18-2018, 06:16 PM   #5
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I bet degraded wiring under the intake. Injector control circuit shorted to the ground wiring.
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Old 09-18-2018, 08:39 PM   #6
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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.
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Old 09-18-2018, 08:40 PM   #7
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Quote:
Originally Posted by dl242gt View Post
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?
Can I get a link to the post? Which connectors we're crossed up in that situation?
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Old 09-19-2018, 01:18 PM   #8
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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.
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Old 09-19-2018, 01:50 PM   #9
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Quote:
Originally Posted by dl242gt View Post
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.
Thinking the 88 740 turbo with LH2.2 doesn't use a cold start valve.
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Old 09-19-2018, 01:52 PM   #10
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Quote:
Originally Posted by Supersneak View Post
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
Have you tried swapping the original coolant temp sensor back in?
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Old 09-19-2018, 01:54 PM   #11
dl242gt
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Good point but it was just an example for the original poster. Not specific to their car.
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Old 09-19-2018, 02:55 PM   #12
Supersneak
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Quote:
Originally Posted by lummert View Post
Have you tried swapping the original coolant temp sensor back in?
Haven't swapped the original back in, that swap was done prior to the tear down with no issues.
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Old 09-19-2018, 04:43 PM   #13
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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
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Old 09-19-2018, 05:00 PM   #14
PromiseRing
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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.
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Old 09-20-2018, 11:20 AM   #15
ZVOLV
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Unplug the ECU. Does the short go away?
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Old 09-26-2018, 07:31 PM   #16
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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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