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mpeterson

91 Ls400

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I just bought a 91 LS400. the thing ran for a little bit then started to have a rough idle then died about 24 hours later. there is no power to the fuel pump and fuses are good i used a jumper to test the pump and the pump works but there is no power at the wires... but even with the pump on using a jumper the car still wont start it cranks and has spark... I'm thinking the IGNITION MODULE? just wanted some input though before i drop the three hundred for the module Thanks Guys!

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Its a bit strange you didn't see power to the FP but when you jumper it to 12VDC the car still doesn't start. Its hard to imagine the FP and somethng else failing at the exact same time. Just too much of a coincidence in my mind. Maybe go buy a low cost fuel pressure gauge and measure fuel pressure at the injector rail just to be sure you have fuel pressure during crank. Since you seem to believe you have spark then I'd stay on the fuel trail a bit longer. Can you get the car to catch at all with some starter spray in the air intake while cranking. If so that might suggest ignition if fine but fuel starvation is at the root of this.

Having said this these cars are famous for one bank of distributor/coil going dead turning the engine into a 4 cylinder and dumping a lot of unspent fuel into the exhaust system. Generally the car will run with 4 cyliners but be very rough running and little power.

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Thank you i will get on the pressure test and go from there...do you know what the pressure gauge should read? the power issue for the fuel pump still gets me there is power coming out of the fuse box but somewhere between there and the FP its lost the power is there and other fuses or solenoids along there?

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This document is pretty good:

www<dot>autoshop101<dot>com/forms/h22.pdf

If you have a Harbor Freight tools in you area they sold a fuel gauge kit for under $20....

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Hi,

Get the fuel pressure test done 1st, if you have a spark it is unlikely to be the ignition/ignitor module as this generates the spark pulse to the coils,as another member suggests remove the air filter and while someone cranks the engine spray some ether/easy start type product into the filter casing,if the engine runs albeit roughly this would indicate a fueling problem.

There are several other reasons why an engine won't run but try the above 1st and then go from there.

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ok so i tried the ether today couldn't get my hands on a gauge right away. there is spark but with the ether no kick at all. i talked to the previous owner i guess the timing is on after it skipped two teeth. really wondering why there was no kick even with spark and ether?

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ok so i tried the ether today couldn't get my hands on a gauge right away. there is spark but with the ether no kick at all. i talked to the previous owner i guess the timing is on after it skipped two teeth. really wondering why there was no kick even with spark and ether?

...."after it skipped two teeth"... do you mean the timing belt is damaged and the timing of crankshaft to cams is off by two belt notches? if so that must be fixed...

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ok so i tried the ether today couldn't get my hands on a gauge right away. there is spark but with the ether no kick at all. i talked to the previous owner i guess the timing is on after it skipped two teeth. really wondering why there was no kick even with spark and ether?

...."after it skipped two teeth"... do you mean the timing belt is damaged and the timing of crankshaft to cams is off by two belt notches? if so that must be fixed...

no its on time now it was fixed after it skipped... the timing belt looks fine as far as i can tell

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