mercedes84

No Spark/fuel Issue After Starter Change

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My starter went out (1991 LS400), once I replaced it I had no fire or fuel. Here's what tests I did. First on EFI upper left 12v, upper right 3.5v, B+ .15v JUMPER to B+ efi upper left 12v, upper right 12v, no fuel pump relay voltage JUMPER to B+ and FP dataport efi upper lt 12v, upper right 12v, fuel pump relay 12v.........Basically with jumper to B+/FP dataport car would start but run poorly with some light back firing......Any help would be appreciated, thanx in advance

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Welcome Michael. It is most likely just a connector that needs put back together. Go back over everything very carefully and I think you will find either a disconnected connector, not fully pushed back together or perhaps damaged when removed. Think simple.

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How was the car running before the starter went out? Was it displaying this same behavior?

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No issues, it ran almost like new. I didn't think think there would be many things involving the B+ area, from the main relay to EFI to B+ and fuel pump. Am I maybe missing something else

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I have gone thru the starter replacement before and know that there are a lot of connectors to put back into place. Miss one and it may not run correctly...just as you are witnessing. Again, go over every inch of the wiring harnesses and double check connections. Assume nothing, check everything.

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post-41820-0-03922500-1439034313_thumb.j

This was posted in another thread on here. It should help explain your problem.

And if this is what you are referring to then either that ign fuse is not contacting good or the ignition switch is not

contacting good. Since you said it only says 3.5 volts. Now check on the ignition side of the ign fuse plug with the ignition turned on of course. If you get 3.5 there then its either the wire or how it connects to the fuse plug or to the ign switch or the ign switch itself. Or the fuse feeding the ign switch or the wire and or connections.

Some place where I just talked about is the problem. But this maybe for a 90 to 92 I don't think 93 is too much different.

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Mine is a 1991, also thx because that info helps as far as what area to look at and start doing some voltage readings.

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I want to be clear, when you say ignition switch you mean the ignition key switch that cranks the car right. I know that may be a stupid question but sometimes a switch could mean a different area maybe under the hood or lower down on the steering column or something. The main relay and efi relay are good (i swapped efi relay with horn and it worked fine)

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Yes I meant the key switch, and the security system disables the starter.

You need to look into the wiring to the cam and crank sensors, and do the igniter test. Make sure the coils are plugged in etc.

If the ecu doesn't get various signals it just shuts things down. Its not going to turn on fuel and spark till the inputs are satisfied. And for fuel and air the cps's are the main signal source. You didn't work on things with the battery still connected did you? Huge no no and will mess things up.

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All of the dash is lit except the cel, which is why no b+....could a faulty ignition cause this issue

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Again, fuses and relays good, all dash lights on except no cel and no 12v to B+ or to FP in Data port, but with 12v jumper from battery to B+ and FP I get cel in dash and car attempts to start but sputters. That's why I asked about the ignition switch, main fusable link or any other short that may send power to the pcm. I think my mind is in the right direction but just a little more experienced help I believe will get me over this hurdle, thx

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Just trace on that diagram back from B+ to the battery something in that path is not right. Ig switch is a suspect yeah so are wires and connectors, fuses, contacts in connectors for fuses, corrosion on wires to the connectors its just so many things I can be. It can be a night mare trying to find the problem.

And the good thing about a diagram is it at least shows you where to start looking and trace back to.

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  • Update. Today I found a ECU at the boneyard, same year as mine. My engine light came back, flashing constantly (meaning no stored codes) but the problem is the fuel is old and smells really bads and the car is not starting but trying. when I spray starter fluid in the throttle body it runs strong as long as I spray but shuts down when spray stops. The fuel pump is running jumped out at the data port but still won't start and run without the spray fluid. Could my injectors be clogged since the fuel is old and smells so bad, maybe the injectors are gummed up. Any input please

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Last time.... check connectors around the Fuel injector system/manifold area. Thats probably all it is if it was running fine before.

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