90 240: eng cont / fuel pump fuses keep popping

[elvis240sx]

Ok, I bought a 90 240 that someone else had swapped a dohc engine into. they told me that they had it running, but it died and they couldnt get it running. i bought the car with intentions of an srswap, but wanted to get it running anyway while i save money so i can move it around to work on it.

i pull off a fuel line and see that it isnt getting fuel, so i check the fuse. this fuse looks just as old as the rest but is burned out, so i replace it. car starts up! it starts fine probably 10 times in 2 days with no problems, runs great, drives back and forth in the driveway and garage.

yesterday, i decide to degrease the engine bay to help see whats going on in there. coat with degreaser i used on my other s13, and spray with the hose. about 5 minutes into this, the car dies out. i check the fuel pump fuse, and sure enough it is blown. i put in a new fuse, and it happens again. i figure maybe something is wet so i call it a night

today, i put in a new fuse and it pops. i check the fuse called "eng cont" and it is blown as well. im not sure what this fuse is for. so i ran a few tests and here are my results.

key on/engine off - speedometer goes crazy, up and down sometimes just for a second, sometimes until the fuses blow. both fuses blow, very quickly. fuel pump and eng cont fuse blow. i even watched a fuse melt in the eng cont, which seems the pop the quickest.

key on/ engine off with fuel pump harness unplugged- eng cont fuse blows quickly, fuel pump fuse does nothing.

key on/engine on- eng cont andf fuel pump fuse blow. sometimes speedo goes crazy, sometimes not

all of these tests were completed with the underhood relays the car came with, and also with the relays from my other s13. when the fuses pop, i still get power to their slots.

this car was running before he did the engine swap but the head gasket went bad so the engine was swapped, which lead me to beleive something underhood or in his ecu wiring is bad. the dohc engine he put in was out of a different car he stripped and also running beforehand.

i took apart all of the harnesses on the underhood fuse panel and cleaned them really well with electromotive cleaner and it didnt help at all. everything in the cabin still works when these problems occur, ie windows/locks/heat etc.

again, this problem didnt occur for me until i degreased and got the engine and wiring wet underhood. about 4 minutes into hosing, it all started. the fuse i originally pulled out was dirty and dingy like the other, and still had the original fuse look to it. i mean, the metal in the middle was like a letter U, whereas whenever i buy fuses the middle is usually a letter z or zig zag shape. where should i start looking to find out what is wrong? how are fuel pump and eng cont fuses related? what is eng cont anyway? my major concern is that after i do the swap, this problem will still exist and I wont be able to find it. thanks for any help!

[NISTECH]

this is gonna be a bugger to find since he had to likely swap all the wiring out of the other car to get this one to run. start checking the harness along the valve cover very closely especially at the rear of the valve cover. look for any where under neath for wear through to the valve cover.

[elvis240sx]

is it foolish of me to assume that the problem lies strictly in the engine bay wiring? oh well, i guess ill get started haha, thanks for your help!

[s13sr20chris]

water and engine bays dont mix. we get cars in every so often wish shiny motors and driveability issues. if fuel pump fues doesnt blow when the pump is disconnected then it sounds like the pump is shorted(or somewhere south of the connector). that is unusual. that is the way to diag though. unpluging stuff can quickly cut down the amount of circuit that you need to check.

[elvis240sx]

how are fuel pump and eng cont fuses related? what is eng cont fuse anyway? thanks

[NISTECH]

engine control fuse handles the power to many of the computer controled/monitered sensors. The fuel pump fuse shoul dbe unrelated to any of those circuits. Did you check the harness at the end of the valve cover?

[elvis240sx]

i couldnt find any bare spots in the harness at all. i screwed down the ecu tonight because it was rattling around for some reason and then i changed the fuses and decided to give it another try. well, it hasnt burned any fuses at all and runs well. i drove it down the road without any problems! now, the speedometer doesnt work. i swapped out the speedo from my other s13 and it worked. sometimes when i turn on the car my speedo works, sometimes it doesnt. i guess its time to buy a new one :/. thanks for you help though, i guess it was just a spot that got wet and shorted some stuff out until it dried. im kind of nervous now since it could happen at any time i guess.

[Altiman94]

it's probably he speed sensor in the transmission. check the wiring to that and make sure everything is in tact

[s13sr20chris]

i hear ya on the speedo. my car was once a flood victim(the car i canibalized for parts, not the one that runs) so the speedo and tacho were both shot. the speedo actually works but sends no sig to the odo. oh well, stuff to fix along with the tailshaft seal, piston rings, wasted tires, wasted shocks, etc.

[elvis240sx]

ill check the wires running to the transmission tonight, maybe ill find something. its weird because with my other s13 speedo it worked fine, but then again maybe it was just coincidence because the "bad" speedo works sometimes too. oh well, ill look into it. thanks!