Fuel pump issues...

I have a 1990 240DL that has sat for a couple years. The gas turned to
varnish so I had the tank cleaned, bought new fuel pumps, sending unit,
gas cap and a few other small items to complete the repairs.

My problem is that I'm not getting voltage (current) to the pumps. I
replaced the replay a few years back and it clicks when the key it
turned to position II. I also have an extra LH-Jet computer. The car
has ran in the past before any of the repairs were done, and nothing
has changed other than it sitting for so long.

I need ideas as to what to check. I've read a lot of posts here and
tried most of the things that applied, but haven't found a solution.

Any help is greatly appreciated.

Fossil Rock

 

The relay can click and still not supply power. The typical problem is
cracks in the solder connections on the circuit board inside. If you have
good eyes and good light the cracks are visible as dark hairlines around the
solder meniscus on the leads of components, especially the heavier ones.

I don't know what sort of fuses your '90 has, but if it has the round fuses
you probably should take them out and buff up the contact surfaces on the
fuses and holders with Scotchbrite or similar. Also check over the
connections at the battery cable - in 700 series cars a few have had a wire
corrode completely in two and cause the fuel pump not to get power (although
the fuel pump relay doesn't cllick under those conditions). Still, worth a
quick peek.

Mike

 

How do you know you are not getting voltage to the pumps, have you
tested with a test light or VOM?

If so, and if it shows voltage from the positive wire, check and see if
the black wire has a good ground; if it doesn't, check and correct the
ground fault.

 

The relay is still in new condition. I checked for bad solder joints
but everything looks fine. My next question is; what triggers the
replay to send current to the pumps. I crossed 30 & 87/2 and the
voltage showed up at the pump leads. When the relay is installed and
the key is turned to the II position the left coil energizes but the
right one (30 & 87/2) does not.

What energizes the other (right) coil?

 

I'm using a DVOM to test with. New copper fuses, cleaned ground
connections. I'm a little confused as to what could be preventing the
replay from energizing the side that feeds the pumps.

 

I think I may have discovered my problem.... stupidity

I was using the spare LH-Jet which was not mounted to the car. I
plugged the original back in, which is still mounted, and both sides of
the relay are energizing now.

Thanks for the replies and keep your fingures crossed for me.