412 LS fuel pump issue.....

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nick sparrow
Posts: 104
Joined: Wed Oct 24, 2001 1:01 am

412 LS fuel pump issue.....

Post by nick sparrow »

Hi everyone been a very long time since i was last here,
my 74 412LS running d-jetronic injection has been in storage for just over 14 years I now have finally got it back on my drive to finish getting it back together. The car has been started several times a year since being in storage last time being late October 2018 it started and ran well. Now i have an issue in that the pump primes the system for 1.5 to 2 seconds but once you turn the key to start the pump stops running and hence no fuel pressure . I have cleaned out the petrol tank and it has fresh petrol all points and spark plugs cleaned and checked, spark is good. I have forgotten a few things but do not remember this being a issue ever before, i have checked all the fuses the pump relay is switching over at least when the key is first turned on I am guessing this could be the relay but have come to a wall in terms of working this out any help would be appreciated. if a can provide more information let me know........

regards
Nick
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raygreenwood
Posts: 11875
Joined: Wed Jan 22, 2003 12:01 am

Re: 412 LS fuel pump issue.....

Post by raygreenwood »

Hello Nick! great to see you alive!

Ok....so when you bump the key...the pump buzzes like it should. That is a function of the ECU having power and the fuel pump relay under the dash having power.
Does it only lose power when cranking?...or will it not stay powered on when in run position and it it actually starts?

Check the white wire from the EFI on the starter....which gives power to the efi on some models when cranking. There is a single wire connecting the EfI relay in the engine compartment (on the ecu in the wagons) and the fuel pump relay at terminal 87 on both relays. Check the grounds of both relays and the grounds on the case centerline first.
Then check the ignition switch for cracks.
Ray
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nick sparrow
Posts: 104
Joined: Wed Oct 24, 2001 1:01 am

Re: 412 LS fuel pump issue.....

Post by nick sparrow »

Nice to hear from you Ray, hope all is well with you will check out your suggestions in the next day or so when i can get a few minutes. the pump primes when the key is bumped and loses power when the key is turned to start; and as not getting fuel pressure it only cranks not really firing as such so its not running yet will get back to you shortly once i check what you have said.....brilliant thanks for your help again......
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