Intermittent Start but runs good when it does

[Beef_Cocaine]

I have a 91 7.3 n/a. Cranking but only starting once in a while. It has an e pump. Replaced all the orings and return lines to the return tee. No air coming out of Schrader valve. When I crack a few lines at the injectors plenty of fuel coming out. Tested the GP relay and harness along with GPS and is working. Plugged block heater in and put heat gun in intake still no start. Disconnected the GP relay and the other day and gave it a tiny shot of ether, fired right up. And once it is running it runs fine. At a loss for what the problem could be. Hoping someone here might be able to help. I'm in remote Alaska and unable to take it to a shop. Thanks in advance

 

[ihc1470]

So what is the temp in remote Alaska at this time? How fast is the starter cranking the engine? What is the battery voltage after you crank it for 15-20 seconds? Based on what you have said about the glow plug system, block heater, and hot air in the intake, along with the fact you say you have fuel at the injectors and the fact it starts with ether. I am going to make this guess.

Almost sounds like the engine is not cranking fast enough to start. I had a loader tractor that I had issues with all winter, when I wanted to start it I needed to give it a shot of ether. Finally had time to look at it. Starter was bad. Replaced starter and it again starts without using any starting aids. Last summer in July the 7.3 didn't want to start very well. It would crank but just would not take off. This was with a warm engine. Again starter was bad. A diesel has to spin fast, not just roll over if they are going to start.

What testing have you done on the starting system? I think that is where I would be looking next. Load test batteries check cables etc.

 

[Beef_Cocaine]

I have a new starter coming, just takes a while to get where I live. Temps here right now are mid to upper fortys. I'm hoping it is the starter. Cables all look good. Cleaned them up when I got it here. It is an old ambulance and has much beefier cables than anything I've ever owned. Ijumpered my dodge up to it and still not starting. No one has a load tester in town, might just order a couple new batteries on the next barge.

 

[franklin2]

While you are struggling to get it started, keep and eye on the tailpipe. If you have lots of white smoke coming out of the tailpipe, that means you do have fuel. If you have fuel and it will not start, there is not enough heat in the cylinders, to light off the fuel.

Glowplugs add heat, your hair dryer adds heat. Compression adds heat. Cranking speed affects compression. If the starter doesn't fix it, then you might have low compression

 

[IDIBOBS]

How exactly did you test the plugs? Did you ohm them or actually watch them get glowing red? Thats really the only way to test for sure. Use the jumper cables on the center of the plug and another on the end. Do not touch the plug. Many times glow plug ohm just fine but no not work at all.

 

[ihc1470]

Can I assume you have a volt meter and maybe a test light to work with for testing?

 

[Beef_Cocaine]

I have a multimeter and test light. I ohmed them but did not pull them to see if they are glowing.
I didn't look at the tail pipe but I will today along with pulling GPS to look for glow.
If no white smoke could that mean I still have air intrusion?

 

[ihc1470]

So do some measuring of voltages then. Start with the batteries. If you have been cranking a lot you would need to charge them up first. Anyway with fully charged batteries what is your voltage reading. Then turn on your lights and HVAC system for maybe a minute turn off and then let it sit for a few minutes and remeasure voltage what do you have. This should give you a reasonable idea the general condition of your batteries. After the minute of loading run your hand over the battery cables and connections, what you are looking for are warm spots that would indicate a high resistance area. Resistance causes heat and poor cranking.

Do you know the history of this truck? How many miles on the present fuel system. How has it started in the past and is this something that has slowly come on it did it show up all at once.

No or little white smoke usually means no or little fuel, it also takes some heat to make the fuel smoke so sometimes a judgement call.

How fast do you think the engine is spinning?

 

[Beef_Cocaine]

History, it was a emergency response rig for the Alaska railroad. I assume it was serviced regularly being with the railroad but don't know for sure. It has 78k on it but not sure how many hours of track time (it has the drop down railroad wheels). It has built in shore power with battery charger which I keep plugged in.

I'm working this morning but will run all the tests suggested this afternoon or tomorrow. Before I put it on the barge it started in Anchorage. I had the local diesel shop put new GPs in it before shipping out.

Thanks again for all the help. I really like this truck. Like I said once it's running it runs great.

 

[Beef_Cocaine]

Had time on my lunch break to start it and look at exhaust. No white smoke or any color coming out when cranking.

It seems slow to me. I have a dodge Cummins and feels like it cranks over 2-3 times faster. I checked the Schrader while cranking and no air with good flow coming out.

Will get back to full test list tomorrow

 

[Beef_Cocaine]

Quick follow up to see if it means anything. Cracked an injector line on last two cranks. No fuel coming out.

Gave it a split second whiff of ether and fired right up.

Do these engines need to crank fast enough to get fuel into and out the IP to start?

 

[IDIBRONCO]

Almost sounds like the engine is not cranking fast enough to start.

That's my guess too.

No one has a load tester in town, might just order a couple new batteries on the next barge.

You could order one of those too.

Do these engines need to crank fast enough to get fuel into and out the IP to start?

No. All they need is for the fuel **** off solenoid (FSS) to be working properly.

 

[Beef_Cocaine]

Working on the list. Went through the glow plugs yesterday. They all ohmed out good. Past the test light test as well. I tried to test for cherry but the relay is not working now. So now I have to wait for that to show up in the mail.

Is it okay to jumper the replay to make sure the harness and plugs are good?

 

[ihc1470]

Well you will be pulling about 200 amps if you try to light them all at the same time. Take a pretty heavy jumper to do that. If you are trying it that way I would suggest just doing on at a time going through the harness. If it test good them remove from harness and connect another until you get all eight done. Easier to just take a couple of 12 gauge wires positive to connector and ground to body going to a battery of course. They heat up quite fast if they are good.

You can use your ohm meter to check the harness.

 

[IDIBOBS]

So like I said take a jumper cable attach black to battery ground and put the other side of black on the body of the glow plug. Then, while holding it with the jumper cable clamp touch the connector to the red on battery. It will get red very quickly. Also first post said you have plenty of fuel to injector. Then you say no fuel to injectors? Do you have fuel at injectors or not? Stop using ether you’re going to blow it up.