Transfer Pump Problem

Last summer our 2000 Monaco Diplomat started a won't start issue. I have had several mechanics want to change out parts to try & fix. What happened was we pulled into a RV Park shut off the engine & stayed for several days. On the day we were to leave the engine would turn over just fine but would not start, this was Sunday no service to be found. It acted just like there was no fuel. Our transfer pump is electric & is supposed to get fuel to the head & the road pump is to take over after starting. We spent one more night & but looking for fuses that might be blown, wire disconnected, found nothing out of order. The next morning around 10:00am I tried to start & it fired up just as usual, not running rough just purred. Drove home over one thousand miles with no problem in starting at all. Put the MH in storage parking & it sat for a few days & wanted to get this issues resolved & went to start & it would not start once again. Called local mechanic & he said to leave key on & cycle the transfer pump a few time, it started after that. The shop looked & tested but found no problems except draining my wallet. Drove several hundred miles started just fine every time. Last Tuesday brought up to the house to restock some items & it would not start even when cycling the transfer pump more then several times. Had a tow truck take to mechanic & they put a high pressure gauge on the transfer pump to read if the pump was working, it had no pressure. The mechanic went back to MH & it started right up 200psi on gauge. I got there & told them to put a low reading gauge on the transfer pump & it had about 5 psi then climbed to 10psi when cycling & not trying to start. Found a new pump & almost put on but after looking at the new pump seen 3 bolts that connect it to the main support bracket with a gasket. I asked them to check the tightness on the 3 bolts on the transfer pump & they got one & 1/2 half turns on each & found that the looseness was allowing the pump to get some air & leak some times causing the dreaded won't start issue. After tightening the transfer pump jumps to 10psi on cycling & not trying to start. Saved $435.00 on pump not being purchased. If you don't watch every thing that goes on you may have a major wallet drain.

Sad that those "mechanics" seemed to have little practical knowledge.  Fuel lift pumps are pretty basic stuff on a diesel!  Maybe not diesel-trained, or perhaps their training was only in "swapping parts" with only superficial diagnosis?

Anyway, good that you stayed on top of it and found the problem.  Maybe next time, just DIY.

I'm not sure what engine you have, but on Cummins, I've read a lot about carrying a $130 spare transfer pump, and wiring a pressure switch in the line from the transfer pump to the main pump that goes to a light in the drivers area. No light, no pressure, stop the engine. From what I understand, if the transfer pump fails, it can cause a failure on the high pressure pump which is $$$ to replace.