(Another) Problem with 1976 Onan 7.5 KW MDJE

[sgharford]

Hi Guys, I plan on troubleshooting, and God willing, fixing a problem that manifested itself about a month ago with my 1976 Onan 7.5 KW MDJE generator. I noticed when I got back to the dock one day after a long cruise that the AC voltmeter was jumping around and generator engine was surging. I had it powering 2 x 16,000 btu's for about 4 hours while cruising. When I try to start now, it get's just on the cusp of turning over, you can hear it fire one or 2 times, then nothing like no fuel. I checked the fuel lines and all seems tight. I retrofitted with electric fuel pump that I tested and is working. I think it may be the centrifugal start switch and going to start there this weekend. Any other ideas? This thing is tucked away, with sound shield, and sooner I can fix problem less likely I will pull a muscle. Thanks All - Scott

[gbharrington]

Filter?

[Regal2800]

You might also want to check the shut off solenoid. I forget whether the solenoid gets power or shuts power to the solenoid once the engine starts running. But if there isn't a change in power to the solenoid the engine will shut off as soon as u release the start button. I had a similar problem on my gen and found it to be a faulty solenoid.

[Steve Barz]

[QUOTE=sgharford;278375]Hi Guys, I plan on troubleshooting, and God willing, fixing a problem that manifested itself about a month ago with my 1976 Onan 7.5 KW MDJE generator. I noticed when I got back to the dock one day after a long cruise that the AC voltmeter was jumping around and generator engine was surging. I had it powering 2 x 16,000 btu's for about 4 hours while cruising. When I try to start now, it get's just on the cusp of turning over, you can hear it fire one or 2 times, then nothing like no fuel. I checked the fuel lines and all seems tight. I retrofitted with electric fuel pump that I tested and is working. I think it may be the centrifugal start switch and going to start there this weekend. Any other ideas? This thing is tucked away, with sound shield, and sooner I can fix problem less likely I will pull a muscle. Thanks All - Scott
"Hunting" Sounds like fuel to me, but here is my take shooting from the hip.
Check fuel system( PRIMARY FILTER) feed & return lines all the way to the tank.
confirm gen fuel tank has fuel, and return tank IS NOT 100% full.
diesel tanks should only be 90% full at max..
a trick I use, iam in the bis, is to use a 3/8"outboard primer blub.
with a piece of 3/8" fuel hose. check flow arrow on blub and connect hose to feed line just before fuel pump, other end of blub in a gallon plastic water jug that's clean and dry, KEEP squeezing the blub.it should be a steady stream of fuel for most of the gallon. blub should be firm to squeeze.
you can also see contamination and water in the fuel, let it settle and check bottom of bottle.
sometimes I do more than a gallon to make sure.
if you pass that test. Clamp the blub inline before the lift pump with 2 pieces of hose.
Then squeeze the blub several times, look around gen for leaks. if you pass that test.
Try to start the gen set and at the same time keep squeezing the blub.
if it starts and runs fine, stop squeezing, if it hunts, squeeze, if that corrects it make sure you ck. gen under LOAD after your done with repair. if not fuel.
CRANK engine over and at the same time, jump the centrifical swich, with a small
screwdriver, just till it starts, then remove screwdriver. The switch is to let the engine build up suf ficient oil pressure before it jumps up to 1800rpm. If it is the switch. I put a adjustable oil pressure switch in the oil system and by pass centrifical set at 12#'s.

[Steve Barz]

[QUOTE=Steve Barz;278405][QUOTE=sgharford;278375]Hi Guys, I plan on troubleshooting, and God willing, fixing a problem that manifested itself about a month ago with my 1976 Onan 7.5 KW MDJE generator. I noticed when I got back to the dock one day after a long cruise that the AC voltmeter was jumping around and generator engine was surging. I had it powering 2 x 16,000 btu's for about 4 hours while cruising. When I try to start now, it get's just on the cusp of turning over, you can hear it fire one or 2 times, then nothing like no fuel. I checked the fuel lines and all seems tight. I retrofitted with electric fuel pump that I tested and is working. I think it may be the centrifugal start switch and going to start there this weekend. Any other ideas? This thing is tucked away, with sound shield, and sooner I can fix problem less likely I will pull a muscle. Thanks All - Scott
"Hunting" Sounds like fuel to me, but here is my take shooting from the hip.
Check fuel system( PRIMARY FILTER) feed & return lines all the way to the tank.
confirm gen fuel tank has fuel, and return tank IS NOT 100% full.
diesel tanks should only be 90% full at max..
a trick I use, iam in the bis, is to use a 3/8"outboard primer blub.
with a piece of 3/8" fuel hose. check flow arrow on blub and connect hose to feed line just before fuel pump, other end of blub in a gallon plastic water jug that's clean and dry, KEEP squeezing the blub.it should be a steady stream of fuel for most of the gallon. blub should be firm to squeeze.
you can also see contamination and water in the fuel, let it settle and check bottom of bottle.
sometimes I do more than a gallon to make sure.
if you pass that test. Clamp the blub inline before the lift pump with 2 pieces of hose.
Then squeeze the blub several times, look around gen for leaks. if you pass that test.
Try to start the gen set and at the same time keep squeezing the blub.
if it starts and runs fine, stop squeezing, if it hunts, squeeze, if that corrects it make sure you ck. gen under LOAD after your done with repair. if not fuel.
CRANK engine over and at the same time, jump the centrifical swich, with a small
screwdriver, just till it starts, then remove screwdriver. The switch is to let the engine build up suf ficient oil pressure before it jumps up to 1800rpm. If it is the switch. I put a adjustable oil pressure switch in the oil system and by pass centrifical set at 12#'s.

[34Hatt]

Like others said fuel remember a lot of times fuel pick up is higher than engines, check and make sure start stop is engaged 100%.
Also remember not to do a lot of cranking without removing plug on the aqua-lift or shut off the intake water don't drown it. Sounds like a good weekend to work on the boat since boating is a no-go.

So maybe just fill a cooler and invite our Long Island diesel expurt over

[sgharford]

Thanks Guys! I'll be sure to check the Stop Solenoid as well as it sounds like Regal2800 had similar symptom. I'll also give the fuel system a more thorough check if start switch and solenoid appear OK. Will report back for closure

[34Hatt]

Scott

I remembered one problem I had many years back it was hunting and when I open the hatch I could hear the stop solenoid kicking in and out was a loose connection fixed it and all good. With your sound shield you may not be able to hear that. Something else to look at the solenoid has spade connectors not he most Ideal connection good luck.

[sgharford]

Thanks Dan! Reckon I'll be turning her around in the slip so the bow faces the waves and doubling up on some lines while I'm down there

[sgharford]

Looks like the electric fuel pump I installed a few years crapped itself (facet model 60106). Though it was OK as I checked with ohm meter last time, but turns out it ain't pumping anything. I just ordered new one and will confirm once I install. Stop solenoid appears to be working correctly per the operators manual.