We have an off road vehicle with an LS376-525 crate engine installed.
The ECU is a MoTeC M130.

Engine cranks, but will not fire. We have spark and fuel. We have installed new batteries, and a new starter. It cranks a little slower than before. But it should start, right?

The vehicle has about 50 hours run time on it, with no previous problems. It was taken to a paint shop, where it has sat for 3 months. Now it will not start.

Did an ECU Live event with Hutter Performance, in Chardon, OH. They did not see anything wrong with the ECU. Hutter has never seen anything like this before.

Any ideas on what the problem might be?

 

Well, you only need 3 things for it to fire - spark, fuel, and air. If you're sure you have spark and fuel, it's hard to believe you don't have enough air to make it fire.

Usually what I do if I'm completely stumped is shoot some starting fluid in the intake while it's cranking (hold throttle cable open at the throttle body with your thumb and release as soon as it fires). If it doesn't fire with that, you have a spark issue.

With it sitting, my first guess would be something with the fuel system - clogged filter, clogged injector, bad fuel.

 

The fact that went to a paint shop is the direct problem. I have idea how they do it, but painters fubar every engine they touch. Have seen it so many times it needs its own meme. Did they do any welding on vehicle when it was there? If so, guaranteed they didn't unplug anything. I am positive they ran the battery down over and over again. May have fried the ECU or sensor(s). When you plug into the ECU, see if it's reading crank/cam signals. If it is and it's not firing, look at the injector drivers. If it got major painted, look for bad grounds.

 

We pulled one spark plug and tested for spark. Sure enough, we have spark. The fuel is 100 Octane, and it is not contaminated or bad. I know we have fuel flow because I could smell the odor of raw fuel coming out of the exhaust.

 

The ECU is good. We installed brand new batteries, and a new starter.

Going to direct jump the starter next visit, and see if that helps. It cranks slow now, much slower than before.

 

Cranking much slower with a new starter and battery is a huge red flag. Pretty much guaranteed some wire connections (probably grounds) were disconnected and then bolted back over paint.

 

Yup!.

I'm not familiar with Motec, but if it needs to see a certain cranking RPM before it will start and it's cranking over slower than before...

Personally, I'd unbolt every ground and use a file or something to take any paint off.

 

Cranking voltage... That's what volt drop tests are for.

 

Yes, and we did that. The volts drop from 12.2 down to 8 during cranking.
We put a booster on the battery, getting 13.4 volts, and dropping to 9 volts during cranking.

 

Cranking voltage drop is a ground issue. Go over all the grounds. Either they painted it or left it unbolted.

 

Going to do that this week!

 

Yeah, without a log everybody is just guessing but visiting a paint shop tells me you have an issue with grounds, etc.

Take a log and watch Engine State, Engine Crank, Engine Sync State, Ignition Outputs, and Fuel Outputs, and Warning Source and see what those say and it will tell you what is happening. If it ran before and it doesn't now it can only be a handful of things.

 

We did an ECU Live event with the engine tuner. He saw nothing wrong with the Motec, or the sensors.

 

What about ref and sync?

I have an m48 with an SBC. I am not very experienced, but I did get it running.

 

I don't know him or his experience but I just gave a list of things that you can look at in the Motec itself.

 

Trevor at Hutter is a good friend of mine and does a lot with Motec.

 

Trevor did my engine tune, and I purchased the ECU from him. Great guy!

 

id remove every ground and power cable, clean and reinstall. its very possible they put them back on hand tight, which will pass a quick visual inspection and show correct voltage with no load and then drop bad as soon as there is any current demand.