Turbocharger Advice

**Ziney** · 12-12-2018, 07:46 AM

I have a pair of Cummins Turbo Diesels (6BTA 5.9-M3) https://mechanicfaq.com/turbos-for-5-9-cummins/ with a hard-to-find problem. Advice appreciated.

Everything was fine in the morning, cruising at 2,500rpm/25kts. Tied up for 2 hours over lunchtime. On return trip both engines refused to rev past 1,500rpm/9kts. Would go to 1,500 at one third throttle position, but moving throttle after that would not result in any more revs or speed.

Things checked so far:

- I did not fuel up that day. Last refuel was followed by several hours of successful boating so bad fuel is unlikely.

- No noticeable smoke. No weird vibrations, noises or smells.

- We have checked fuel screen and filters, which are OK and correctly specc´d

- Checked throttle mechanisms, which are OK

- Engines are turbo-charged and we did have issues with one of the turbos not spooling up so we have overhauled both turbos. No improvement.

**Motv18** · 12-12-2018, 01:04 PM

Boost gauge?

For me I would check the whistle. Whistling like normal probably means good boost.

Maybe check fuel filter algee can just suddenly sprout. Especially if you got some bio or water.

Did rpm come up like normal to 1500, all cylinders hitting good, boost is usely built by 1000 rpm

any system that would fault and limit rpm?

**FORBESAUTO** · 12-12-2018, 03:03 PM

Being both engines acting up, would think it’s a common denominator between the two. I would be looking for algae on pick up screen in tank if has one. Keep in mind ya gotta have fuel/ good burn to make heat to get boost also.

**marks86** · 12-12-2018, 04:16 PM

Originally Posted by FORBESAUTO

Being both engines acting up, would think it’s a common denominator between the two. I would be looking for algae on pick up screen in tank if has one. Keep in mind ya gotta have fuel/ good burn to make heat to get boost also.

Exactly! I don’t know much about the topic, but I would start by looking at fuel related items that both motors share

**STV_Keith** · 12-12-2018, 05:20 PM

What fuel pump is on these engines? Do these have the old VE rotary pump like the 88-93 Dodge pickups?

**flabum1017** · 12-12-2018, 08:39 PM

Originally Posted by FORBESAUTO

Being both engines acting up, would think it’s a common denominator between the two. I would be looking for algae on pick up screen in tank if has one. Keep in mind ya gotta have fuel/ good burn to make heat to get boost also.

If it were an air problem,you would have black smoke from one or both engines. So it's either a fuel restriction somewhere or an exhast leak in the engine room. If you have Racor filters, there is a ball in the convalecer that will float on water and restrict the fuel.... Also, loose lids will let air in the filters, well known problem with Racor.

Do you get full RPM when you no-load it?

Do both engines pull from the same tank? If so, could also be a plugged fuel tank vent. If it's a Sea Ray, they have electronic shut off valves near the tank that can get plugged up with algae or trash. You can check for restriction in the fuel line with a vacuum gauge inline before the engine or if you have racors, you can get a gauge kit that replaces the t-handle on the filters. Anything more than 2 - 3 inches in vacuum is a restriction. You don't need to r
take the boat out to test for restriction, just no-load it at the dock.

**flabum1017** · 12-12-2018, 08:44 PM

Originally Posted by STV_Keith

What fuel pump is on these engines? Do these have the old VE rotary pump like the 88-93 Dodge pickups?

All the BTA series 5.9's I've seen in marine use use inline pumps....

**Motv18** · 12-13-2018, 12:29 PM

When was the last overhead as well.

**STV_Keith** · 12-13-2018, 07:24 PM

Originally Posted by flabum1017

All the BTA series 5.9's I've seen in marine use use inline pumps....

So P7100 pumps?

Anything back from the OP?

**flabum1017** · 12-13-2018, 08:03 PM

Coincidentally, I'm working on an 8.3 that idles rough, has low power and blows black smoke at top end... about 400 down. Supposedly 200 hours since total engine rebuild (in Miami

) Pump and injectors are at the injection shop now. Gonna check compression when starter comes back from rebuilder (rusted up from leaky saltwater side of heat exchanger). Turbo looks good, no play, spins free. this engine is quiet when you stab it in nuetral, the other has typical diesel knock...... All the valves were way out of ajustment (loose) and backwards... intakes were like .040 and exhausts were like .015. Hoping they find something in the pump but if they don't, front cover will be coming off.

**baja200merk** · 12-14-2018, 11:30 PM

I would suspect a voltage issue to the shut down solenoid. Easy way to diag is zip tie them up and go for a ride. They use 12v to pull and 5v hold so If there’s a connection or voltage issue it’s more obvious on the 5v.

I like .008/.018 on the 6bta in the truck.

**marks86** · 12-15-2018, 08:15 AM

Originally Posted by baja200merk

I would suspect a voltage issue to the shut down solenoid. Easy way to diag is zip tie them up and go for a ride. They use 12v to pull and 5v hold so If there’s a connection or voltage issue it’s more obvious on the 5v.

I like .008/.018 on the 6bta in the truck.

voltage issue with the Fuel shutoff solenoid would result in the engine dieing or not starting at all. I battled this issue for along time, and as you stated before a simple zip/ peice of wire figured out my problem quickly.

**flabum1017** · 12-15-2018, 08:37 AM

I'll check to make sure the shut off lever is at it's stop in the run position after I get the pump back. Injection shop says pump is fine but the injectors were "iffy" so getting new tips. With all the mistakes I'm finding with this engine, it won't surprise me to find the cam gear off by a tooth. The valves were way out of adjustment and the timing pins were sheared off (whoever assembled this left the pins engaged) I'll try to figure out how to determine if the cam gear is off by a tooth somehow without removing the front cover. Maybe see how many degrees the intake opens. Have the other engine to compare to.

**baja200merk** · 12-15-2018, 09:39 AM

Originally Posted by marks86

voltage issue with the Fuel shutoff solenoid would result in the engine dieing or not starting at all. I battled this issue for along time, and as you stated before a simple zip/ peice of wire figured out my problem quickly.

That’s a more common issue but LOW VOLTAGE like a bad connection can cause the solenoid to only pull up enough for 1/2 fuel = 1/2 power. For it to run 2500 turn off and start back up only pull 1500 sure seems like an easy thing to check. Have seen it happen before.

**flabum1017** · 12-15-2018, 10:31 AM

Originally Posted by baja200merk

That’s a more common issue but LOW VOLTAGE like a bad connection can cause the solenoid to only pull up enough for 1/2 fuel = 1/2 power. For it to run 2500 turn off and start back up only pull 1500 sure seems like an easy thing to check. Have seen it happen before.

Possible, the battery cables are all screwed up in this boat, have to paralell to start this engine. But that does not explain the black smoke at upper RPMs