shibaura s753 diesel engine won't start - - The Friendliest Tractor Forum and Best Place for Tractor Information
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post #1 of 3 Old 07-14-2018, 04:09 PM Thread Starter
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Unhappy shibaura s753 diesel engine won't start

I have a Multi-quip Diesel Light Tower. Basically a motor generator with a telescoping mast with 4 1000W lights at the top.

I bought the Light Tower from my Girl Friends son who runs several athletic fields for soccer. I help him maintain the towers. The one I bought was one he wanted to off load because it was hard to start and a rust bucket. The price seemed right, but I hadn't started it in months.

I towed it home (50 miles). Now at my house, I'm trying to start it and it won't start. I am fairly new to diesels, but I think I'm going after this the right way. Looking for tips:

Here is what I have done:

1. The injectors are mechanical. The engine turns over good, but I have had some other tower engines that seemed to turn over ok, but wouldn't start until I put a new battery in them to make them crank just a little faster. On this one I connected my battery booster so I think it is turning over fast enough.

2. These have safety cutouts for low oil pressure, high coolant temp, and low air flow. I assume that when any of these 3 things are out of spec. it cuts power to the fuel shut off solenoid. I checked power at the solenoid, and NO power. Eureka moment, but applying power directly didn't help in starting, but I believe it did bypass all the safety cutouts.

3. The fuel is pumped to the injector pump via a mechanical pump and there is a bulb squeeze type pump for bleeding air out of the system. I tried bleeding it, got fuel out the return line and a little out of each mechanical connection at the top of each injector. Didn't help.

4. I pulled the output line off the fuel pump and cranked it. Very little output, so I disconnected the in and out and put an electric fuel pump in it's place. I Bled the system with the electric pump at the top of each injector and the return line. I'm getting little to no fuel at the injector fittings.

5. Pulled the shut off solenoid and checked to make sure the plunger is pulling in, and it is.

6. So, here is where I am, It's 100 degrees outside, I have the electric fuel pump hooked up directly to the battery as is the fuel cut out solenoid. I crank the engine over and it spins nice, but doesn't even try to start. I run the glow plugs 30 seconds until the light goes out. I crack lose a connection to an injector and get little if any fuel.

7. I hope the following didn't screw something up. I pulled the discharge lines off of the injector pump and from the injectors. I cranked the engine, and only got a little squirt of fuel from one of the injector pump ports. My logic tells me that something is wrong with the injector pump, unless there is some kind of check valve that caps off the fuel flow when the fuel lines are disconnected.

I'm also wondering if the electric fuel pump is producing enough pressure. Could it be that the mechanical pump is shot, and the electric pump doesn't put enough pressure to the injector pump?

So, I need some advice, I'm really hoping it's not the injector pump, but it sure looks like it is. Oh, and then I thought, what if the engine is low on oil, thinking maybe the pump uses oil for hydraulics, but it's only down 1/2 quart. Any diesel pros out there?

Sorry for the super long post, and thanks for reading. Any help or suggestions will be greatly appreciated.


Last edited by paulcalif; 07-14-2018 at 04:27 PM.
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post #2 of 3 Old 07-29-2018, 10:53 PM Thread Starter
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Re: shibaura s753 diesel engine won't start

I am making progress:

I now have it running. The main problem was the injector pump. I bought a second light tower that ran but has a bad radiator. I took the injector pump from the running light tower and put it into the light tower I've been working on. Started right up with tons of black smoke coming out the tail pipe. I let it run and slowly all of the black smoke cleared.

I had installed an electric fuel pump and bypassed the mechanical fuel pump. Now that I confirmed that the injector pump was bad, I reconnected the mechanical pump and it runs fine.

These engines have a solenoid plunger that shuts the fuel off by moving a bar on the injector pump. The solenoid requires 12v to pull in and allow fuel to flow. There are three safety cutouts that will disconnect the 12v going to the solenoid. High water temp. Low oil pressure, and low air flow.

I'm not getting 12V to the solenoid so either I have a bad sensor(s), or something else is not working correctly and preventing the 12v. to pass to the solenoid. I haven't found a schematic for this particular light tower so troubleshooting beyond checking the sensors my be time consuming.

I hope this helps someone some day. I'm disappointed that no one hear has chimed in and offered any suggestions.
I'll post again once I've figured this out.

In the mean time, I've taken the bad injector pump apart. There isn't anything real obvious that I can find wrong with it, but the mating surfaces look to be slightly worn. Replacement injector pumps are expensive, north of $1000. I am trying to lap the mating surfaces with diamond lapping compound. Not real optimistic, but a set of 5 grits of diamond compound was only $20 so I figured it's worth a try. They go from 30 micron down to 1 micron. Anyone know if that's fine enough? Too fine?
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post #3 of 3 Old 11-25-2018, 04:20 PM
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Join Date: Oct 2018
Location: Indiana
Posts: 252
Re: shibaura s753 diesel engine won't start

If it was mine i'd just bypass the safety's and make sure that when trhe switch is on the shutoff has power and opens.

Isn't there a shop in your area that rebuilds injectors and IP's, would be alot cheaper then a new one.
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