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Burning up fuel pumps

Radtap

Radtap

Well-known member
Joined
Dec 16, 2020
Location
Tucson, AZ
I've got an 80 242 b21 kjet and this thing for whatever reason is destroying fuel pumps like an angry toddler knocking over building blocks. I've inspected as much of the wiring for the pumps and it just keeps burning them. The car sat for 20 years but I've yet to find any indication of packrats or mice in the year I've had it. Today is the 4th pump it's killed and I still can't figure out why. Original pump was long gone when I got the car and so was most of the fuel system, replaced it and after a week of working on it died, figured maybe bad unit, 2nd one burned up and once again replaced it & inspected wiring and found nothing, 3rd one burned up and I replaced the wires coming through the floor with the connectors thinking maybe they had corroded from the inside causing excess resistance or something I'm no electrician and now today when I was hoping to start it for the first time in 20 years #4 stops whining. Luckily I got the pump through amazon and haven't paid for replacements. Anyone deal with something like this? My only thought is that poor degraded harness is causing shorts elsewhere causing the pump to burn up? But I haven't found many shorts and the ones I have I fixed.
 
Is the fuel pressure pump working? The one under the car near the rear tire. The in tank one is a lift pump to feed the second pump. If the second pump isn't working it can kill the in tank pump pretty quickly.
 
2turbotoys said:
Is the fuel pressure pump working? The one under the car near the rear tire. The in tank one is a lift pump to feed the second pump. If the second pump isn't working it can kill the in tank pump pretty quickly.
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Entire fuel system has been replaced and I?ve got a new intank pump and sending unit, I did have some gremlins with the intank pump at first but got those sorted out, the intank pump starts up and goes no problem, the one time I can actually hear it when I don?t want to. It?s my main pump underneath the car that keeps going
 
Usually the problem is the relay burning up, I wired a heavy duty relay for the pumps, it was turned on by the factory relay. That car is now converted to an LS swap.

On my 79 242, I got rid of both pumps and put a Deatschwerks DW200 pump in the tank. The car is converted to Megasquirt EFI, but you could do the same thing I would guess, but hopefully one of our resident K Jet experts checks in here.
 
2turbotoys said:
Usually the problem is the relay burning up, I wired a heavy duty relay for the pumps, it was turned on by the factory relay. That car is now converted to an LS swap.

On my 79 242, I got rid of both pumps and put a Deatschwerks DW200 pump in the tank. The car is converted to Megasquirt EFI, but you could do the same thing I would guess, but hopefully one of our resident K Jet experts checks in here.
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Literally the second I finish building my LH b230 I?m pulling this kjet out and selling it all, I literally hate it with a passion, I was stubborn and didn?t want to remove the intake and I remove and installed the entire fuel distributor setup and lines maybe 4 or 5 times? When I got the car it did have a later LH relay which I think is why the pump burned the first time but I?m not sure, swapped it out for the right one. I can only imagine this is an electrical problem but A) I don?t wanna replace all the wiring just to pull out a majority of it for my LH/ezk swap and B) I can?t visually find any issues with the fuel pump electrical. When I swap the motor I?m going to be moving more fuel since I?ll have a turbo so I?m interested in aftermarket fuel systems or an alternate fuel pump setup. Probably stupid question but there shouldn?t be any real difference between a kjet and a later year LH pump other than the kjet ones coming with the plastic adapter ring right? LH pump is a little cheaper
 
Bosch backs their fuel pumps by a lifetime warranty as long as you replace the fuel sock and/or filter. I replaced mine for about $70 from Rockauto 3 years back.
 
Bought from the Bosch store through Amazon, Bosch box, instructions, crap and all, paper receipt with all the Bosch names and all, sometimes even the original shipping label from the Bosch manufacturer, I’m pretty sure they’re legit Bosch pumps and I trust their product, I know about their warranty but I’m lazy and I like amazon’s system since their drop off is literally next door to my work
 
I had the fuel pump system fuse getting too hot and eventually melting. This was on my kjet turbo. The problem turned out to be the engine wiring harness was causing too much current in the fuel pump relay circuit. It burned up a couple relays as well. I know it seems like the engine wiring harness is unrelated but if your car is a lambda model there is wiring associated with the fuel pump relay that goes to the engine compartment. So, check for decaying wiring in and around the engine. It's probably the problem.
 
Radtap said:
Probably stupid question but there shouldn?t be any real difference between a kjet and a later year LH pump other than the kjet ones coming with the plastic adapter ring right? LH pump is a little cheaper
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There's definitely a difference between K-Jet and LH pumps. K-Jet pumps are rated for 108-188 liters/hour @ 5 bar, NA LH pumps are 100-175 L/H @ 3 bar.

Which pump are you using?
 
dl242gt said:
I had the fuel pump system fuse getting too hot and eventually melting. This was on my kjet turbo. The problem turned out to be the engine wiring harness was causing too much current in the fuel pump relay circuit. It burned up a couple relays as well. I know it seems like the engine wiring harness is unrelated but if your car is a lambda model there is wiring associated with the fuel pump relay that goes to the engine compartment. So, check for decaying wiring in and around the engine. It's probably the problem.
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It is a lambda car, what did you do to fix it? I'll have to go over the harness again, I just don't like touching it cause it only causes more damage

hiperfauto said:
There's definitely a difference between K-Jet and LH pumps. K-Jet pumps are rated for 108-188 liters/hour @ 5 bar, NA LH pumps are 100-175 L/H @ 3 bar.

Which pump are you using?
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Bosch 0580464126 or 69430
I'm pretty sure that's the correct one for my car. I kinda doubted the pumps were the same since I know kjet runs a little higher than efi but wasn't 100%
 
is it possible the in-tank pump is wired backwards? admittedly this happened to me and it was bear to figure out. It never killed my OE main bosch pump tho, just ran like crap.
 
esmth said:
is it possible the in-tank pump is wired backwards? admittedly this happened to me and it was bear to figure out. It never killed my OE main bosch pump tho, just ran like crap.
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I double checked my sending unit when I got it to make sure it was wired properly and as far as I know the in tank pump is working as intended, I can hear it going and I?m getting fuel in the line up to the main pump. Gotta find this gremlin so my main pump stops burning. I?m gonna check the lambda wiring in the bay on Wednesday
 
The main pump can out pump the in-tank pump. Make certain that the in-tank pump is wired correctly. If the in-tank pump is wired backwards it will pump backwards (as in back into the tank).
 
lummert said:
The main pump can out pump the in-tank pump. Make certain that the in-tank pump is wired correctly. If the in-tank pump is wired backwards it will pump backwards (as in back into the tank).
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:nod:

The tank pump will run backwards and make noise as described. the car will still run too
 
lummert said:
The main pump can out pump the in-tank pump. Make certain that the in-tank pump is wired correctly. If the in-tank pump is wired backwards it will pump backwards (as in back into the tank).
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Already confirmed my pump isn?t wired backwards when I first got my new sending unit per flametrap. I also doubt the pump running backwards would kill the main pump what feels like overnight. It?s never died on me while driving, it?s only ever killed pumps when I try to crank
 
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