Genset No Fire/ Fuel Pump

Splashed and was starting all engines. Genset, Onan MDJE 7.5Kw, started instantly, ran 10-15 secs, stopped and would not restart. I will be pulling the primary fuel pump, as I think that is the issue. But before I do in a few days, thought I would post here, for further ideas.

I pulled the water cup, which is integrated with thy primary pump, and found some kludge particles on the cup bottom, but the diesel was clean. So cleaned the cup out, re-filled with fresh diesel, re-installed. I worked the priming arm quite a few times, 20-30+, but the arm never seemed to meet resistance; not sure if it should (?). While trying to re-start, it would fire a tiny bit, but never catch.

My guess is that the diaphram split/tore in the mechanical pump, when I first started, because it ran so well, then stopped and would not restart.

Will post update on results, at later time.

Hard to tell what is happening at this point. If the cam lobe has the pump engaged you will feel no resistance on the lever. Turn the engine 1/2 turn and pump,crack a bleeder or injector line and see if you get fuel. If so,proceed to bleed. If not,look elsewhere. Check in logical order. Fuel in tank? Valves between tank and filter? Lift pump working,etc. They only way to troubleshoot. Good luck.

let us know what you come up with, i have the 7.5 also and is a PITA to get started, and gives off black smoke, my buddy i was tied up with wasn't too happy afer i pulled away from his boat. i did notice the fuel pump is leaking now so possibly sucking air?

Yup sounds like your on the right track. The lift pump has a diafram in it and you should feel a little resistance after about 30 strokes. Rebuild kits are available for the Lift pump as I had to do mine last year. Be careful as you take it apart because there is a lot of small pieces that "spring" out, don't ask me how I know this. After about 1/2 hour you should be done.

Chris
Superior Nights 53C

Quote:

---

Originally Posted by wmfels

let us know what you come up with, i have the 7.5 also and is a PITA to get started, and gives off black smoke, my buddy i was tied up with wasn't too happy afer i pulled away from his boat. i did notice the fuel pump is leaking now so possibly sucking air?

---

If you have a "normal" 7.5, then you should have one starting aid per cyl, i.e. each cyl has a "glow plug". Also there is a "heated coils" unit (I call it the toaster oven) that is in the air intake that serves both cyls. That "toaster oven" has two internal heated coils, either of which can go out (or both). So there are four points of starting aid that may go out, any one of which reduces starting ease.

So if you do it yourself, put meters on the two glow plugs with the Ohmmeter and each should get a reading. Also do the same with the two heater coils, which should have a reading (register a value).

I was frustrated with the Hatt Dealer/Marina Manager who said my Onan "...was shot...", because it started hard and smoked. Those guys gave me lots of bad advice. Actually, it needed a glow plug and a heater coil each replaced. That Hatt manager helped them get one of the poorest reps in the Midwest; I won't be more specifiic, because after 4 attempts (new managers), they seem to now have a good manager (one of their own in-house guys).

Finally, its possible the primary pump is weak as well.

M2CW...

Hoping to pull primary fuel pump in the next couple weeks. One reason that I moved the boat 4 hours closer, so I can give it some TLC, sinced I like to do some hands on. Frankly, where I was before, good techs were very hard to come by. It is super nice to have her closer by.

I had the same problem. I replaced the fuel pump with an electric from napa for $20 bucks runs perfect. I wired it to the started circuit so it turns on when you preheat or start. You never need to fool around with that lever again.

Quote:

---

Originally Posted by ocburger

I had the same problem. I replaced the fuel pump with an electric from napa for $20 bucks runs perfect. I wired it to the started circuit so it turns on when you preheat or start. You never need to fool around with that lever again.

---

As the saying goes, "...did it/does it bolt into place..." of the old/legacy pump, or did you leave the old one in place and mount the new one elsewhere....etc.?

I also replaced my pump with an electric one. The shematic indicates an optional electric pump that is wired to the same circuit as the as the fuel solenoid. I also added an inline filter before the pump.

Quote:

---

Originally Posted by spartonboat1

As the saying goes, "...did it/does it bolt into place..." of the old/legacy pump, or did you leave the old one in place and mount the new one elsewhere....etc.?

---

I left the original in place. The electric pump is about 2" in diameter and 4" long so it looks like a buldge in the fuel line. Comes with a bracket I attached to one of the bolts on the gen vent cover thing. With the correct fuel line connectors probably 30 min job.

Update on my fuel pump, MDJE, 22 Jul, 2012, which a candidate issue area, because in the Spring 2012, she started great, ran 15 secs, stopped and would not re-start.

I finally had time to pull the fuel pump and disassemble it. The diaphram seemed in good order with no signs of cracking; it was replaced in 1994, when the entire genset was rebuilt and has had few hours since. The internal check valves seemed to function well and the screen over the water bowl was slightly dirty, so I cleaned it well.

After reassembly and re-installation, I was able to get good pressure build-up, by working the priming handle. Thanks to the earlier post about cycling the getset to get the primer un-loaded.

She started almost instantly without starting aids, as it has been hot here in MI recently, plus I had run the mains to exercise them, so the ER was warm. However, after running for about 30-40 seconds she again died. I tried the priming handle again and got good pressure quite quickly, but she is reluctant to start.

Next up: replace both fuel filters, which haven't been replaced for about 10 years (no booing please) and try starting again. Also, I will double check if the pump follower is on the lobe internally. Maybe I did not re-install it on the lobe........

I just replaced the mechanical pump on my MDJE over the weekend with a Facet Posi-Flo Low Pressure Fuel Pump Kit, 32 GPH (part number FEP06SV). It's rated for Diesel and Coast Guard approved. I wired it up to stop solenoid and it works like a champ! And boy are you in luck, even have a picture of install. Was going to put a new thread up about it but why not here. Note to run the wires downward from stop solenoid so they don’t get in the way of governor control arm.

The mechanical pump on that Onan has given me gruff since I owned the boat. What I found was a constant leak in mating service where the fuel bowl sits against body housing via the bail. What happened is the flat service on the fuel pump housing went out of true, and even with the thick rubber gasket in place there was enough of a twist to cause a leak to screw it all up. I swear the only thing that can stop a diesel engine is sunction line leak. So $60 for an electric pump and $40 for some fuel line and fittings (I was able to reuse 1 end of fuel line on old pump) and I'm finally done with that bitch pos mechanical pump once and for all! I knocked the pin out of the old mechanical pump that held the cam driven lever and bolted in back in place with pin re-inserted. I also cut the fuel bowl section off main pump body, leaving a hole that a 10mm bold threaded nicely into incase the diaphragm breaks it will still be pressure tight. This also involved capping the fuel outlet side of mechanical pump with ¼” NPT brass plug. You could make a cover plate, but same crud different day if you ask me. Anyway – I think is a much better option the replacing with the $400 pump from M&D mower (the only place that may still has the original pump). Good Luck with it.


edit: To check if your fuel pump is leaking, take it off and pressurize it to 15psi in a tub of water and look for bubbles with the fuel outlet capped off (I used my finger on fuel outlet to cap and a Mity-Mac pressure/vacuum tester on the inlet side to pressurize) It's the only way I know of and will keep you from second guessing if something else. I can't help but imagine how many good MDJE's met their undue demise becasuse of this fuel bowl leak.


Expurts - forgive the yellow electrical tape, it was within arms reach and simply holding a protective wire loom from slipping.
Attachment 11876

Quote:

---

Originally Posted by sgharford

I just replaced the mechanical pump on my MDJE over the weekend with a Facet Posi-Flo Low Pressure Fuel Pump Kit, 32 GPH (part number FEP06SV). It's rated for Diesel and Coast Guard approved. I wired it up to stop solenoid and it works like a champ! And boy are you in luck, even have a picture of install. Was going to put a new thread up about it but why not here. Note to run the wires downward from stop solenoid so they don’t get in the way of governor control arm. The mechanical pump on that Onan has given me gruff since I owned the boat. What I found was a constant leak in mating service where the fuel bowl sits against body housing via the bail. What happened is the flat service on the fuel pump housing went out of true, and even with the thick rubber gasket in place there was enough of a twist to cause a leak to screw it all up. I swear the only thing that can stop a diesel engine is sunction line leak. So $60 for an electric pump and $40 for some fuel line and fittings (I was able to reuse 1 end of fuel line on old pump) and I'm finally done with that bitch pos mechanical pump once and for all! I knocked the pin out of the old mechanical pump that held the cam driven lever and bolted in back in place with pin re-inserted. I also cut the fuel bowl section off main pump body, leaving a hole that a 10mm bold threaded nicely into incase the diaphragm breaks it will still be pressure tight. This also involved capping the fuel outlet side of mechanical pump with ¼” NPT brass plug. You could make a cover plate, but same crud different day if you ask me. Anyway – I think is a much better option the replacing with the $400 pump from M&D mower (the only place that may still has the original pump). Good Luck with it.edit: To check if your fuel pump is leaking, take it off and pressurize it to 15psi in a tub of water and look for bubbles with the fuel outlet capped off (I used my finger on fuel outlet to cap and a Mity-Mac pressure/vacuum tester on the inlet side to pressurize) It's the only way I know of and will keep you from second guessing if something else. I can't help but imagine how many good MDJE's met their undue demise becasuse of this fuel bowl leak. Expurts - forgive the yellow electrical tape, it was within arms reach and simply holding a protective wire loom from slipping.Attachment 11876

---

Excellent reply just five years ago, who was the source of fuel lines for this conversion? Regards, Craig

Just a thought, since you just splashed is it possible the generator is not getting water? They have a over heating shut down built in. Check for obstruction or air lock. Who knows, it might be something simple as that.

First thing I'd check is if the fuel solenoid engages when you push the start switch and STAYS engaged. As they get old they may pull in initially but the magnet won't hold and they pop back out. If it doesn't suck in you can check voltage on the single wire attaching to the top. If you have juice and no solenoid action, you've found your problem.

If the solenoid is working it's time to check further down the line. Crack the line on each injector and crank the engine and verify you have fuel reaching the injector. If you don't, you have a fuel pump issue.

I wouldn't bother fixing the mechanical fuel pump. There are too many items to go wrong in there including check valves, diaphragms, etc. If you want to rebuild one, I will send you one and you can do it on your workbench at home. It's MUCH better to just remove the pump and bolt up a block plate. Interestingly my Onan used the same blockoff plate used on a small block chevy so the plate and gasket were at my local auto parts store for $8 next to all the old school performance items. The proper electric pump was also for sale there and it needs to be the high pressure pump for diesel, not the 5psi pumps for carbed engines. I think it was about $40. I wired mine to the positive wire on the top of the fuel solenoid and had no problems. The downside is it did not energize the pump until you crank the engine so it took about 3 seconds to start instead of instant. I had no complaints though.

Good luck.

Since I started this thread, I definitely owe an answer of findings, since the pump now works well (Summer of 2017). The two primary issues have now proven to have been:
1) The automatic speed management control arm, that is on a pivot, under the raw water pump. I found that it was "stuck" and not cycling, which stopped proper speed management. True story: I gripped the shaft and lifted up on it, freeing it. It has not seized since.
2) The raw water pump stopped pumping and the overheat sensor shut her down (thankfully). My short term cure (see my other thread) has been to insert a 1/32" thick copper shim between the pump cover and the impeller. It ran well at all times since. Please note that I ordered both a new wear plate and cover, which are now installed. We will see how she pumps next season. Note that the original cover plate did have some slight scoring.

Will update next Spring, 2018.