1989 245DL Fuel pump issues

fbisek · Post by **fbisek** » 18 Feb 2015, 20:29

The car has been idling rough for a bit, then two days ago it died after a mile down the road. It seemed like it ran out of gas. I decided to replace the fuel pump relay and the in tank fuel pump. Successfully replaced each and the issue was not resolved. It'll turn over just fine, then about 30 seconds it will start to sputter and die. I decided to mess with the fuses, and it runs much better when I disconnect the in tank fuel pump fuse. Does anyone know what would cause this?

lummert · Post by **lummert** » 18 Feb 2015, 22:21

I hate to be the bearer of bad news but some of the in-tank pumps end up wired backwards. This may be due to the terminals being marked incorrectly. The pump can run either way depending on how it's wired. Wired backwards = pumping backwards.

fbisek · Post by **fbisek** » 19 Feb 2015, 06:43

it was the same model pump and there was only one way to wire the pump in. Is there a way to check if it is pumping the proper direction?

lummert · Post by **lummert** » 19 Feb 2015, 07:40

Info on transfer pump:

http://www.cleanflametrap.com/transferPump.htm

fbisek · Post by **fbisek** » 19 Feb 2015, 10:17

I've checked and the pump is installed correctly according to http://www.cleanflametrap.com/transferPump.htm and there is still an issue. The install guide says to check the polarity of the electrical system. How do I check that? And where?

fbisek · Post by **fbisek** » 19 Feb 2015, 11:22

OK so when i pull the in tank pump fuse the car runs better, but you can tell there is a load on the main pump. But when i pull the main pump fuse the main pump continues to run. Could this be the source of my issues? And what does that mean?

lummert · Post by **lummert** » 19 Feb 2015, 17:57

Trace wires from in-tank pump to relay for short.

fbisek · Post by **fbisek** » 20 Feb 2015, 21:15

Ok so I pulled the tank fuse and drove it for a bit on just the main pump. And put the in tank fuse back in. Now seems to be running well again. May have been some sort of vapor lock in the pump that has now cleared.