4jh4-TE Low Revs

[hpeer]

Stuck on cruise, need advice. Engine will not rev. In small port in Nova Scotia.

Picked up dirt in fuel on passage. Engine would not rev over 1800, which is where I was running.

Have replaced all filters and now have clean fuel, still will not go past 1800. With or without load, no difference!

Local mechanic, who seems knowledgeable, says one injector not working, send all four out for service. Got back and no joy, still stuck at 1800.

Fuel lines are clean, filters good. Removed mixer elbow, normal soot. Ran without elbow with only slight improvement. This seems to eliminate back pressure as culprit.

Turbo seems free.

Now at a loss of what to do. Been reading service manual to little avail.

The one idea I have is related to the turbo. The fuel pump has a "boost compensator" which appears to sense the amount of turbo boost. Perhaps there is something wrong with turbo after all, and I get too little boost? Sounds like it would not cause this issue but I am grasping at straws here.

I hear changing fuel pump is costly, would like to rule out all other possibilities first.

Many thanks,

Howard

Pump markings
Sh 80
129671-51950
104742-7541

[Charlie]

BUMP

I don't know the 4JH4 TE well I have the non turbo version of the same engine. Del Marrey has the 3JH3E (I think). I can help you out a little he can do more.

This is very basic but I will throw this out first. Have you checked the throttle linkage. An easy check is to disconnect the linkage and see if you can run the throttle directly from the engine. If that is working there are two other items that I would check. One is the govenor spring and the second is the lift pump. The lift pump is easier so I will start there.

When you say the fuel pump I feel like you are talking "injector pump." Is that correct? The lift pump -- which sits on the injector pump -- could not be getting sufficient fuel to the injector pump. Have you tried installing a temporary gravity fuel tank? I will explain myself a little here.

First you need to disconnect the lift pump. To do this take a short (12") piece of fuel line and run the fuel line from the intake of the lift pump to the output of the lift pump.

Second you need to run a length of fuel line from a clean fuel source (eg a jerri can) to the secondary filter on the engine. You will need to have the clean fuel source above the engine so it gravity feeds. You will also need to start the siphon to the filter.

If this solves the problem then you need to replace the lift pump. If you can not get the part you can get a small electric diesel fuel pump and wire it in so that it turns on and off with the engine. IT is best to place this after the primary filter.

Ok as for the govenor I don't feel that I am qualified to explain it but there is a good section in the manual on how to do it.

[hpeer]

Thanks,

1 yes, checked the linkage and it is ok, it comes against the high speed stop ay WOT.

2 I will take a stab at your suggestion to bypass the lift pump.

3 correct, by fuel pump I mean injector pump.


My gut feeling is that because it will rev to the same RPM with or with or without load it is likely getting sufficient fuel. Not sure of myself on that logic. I did recheck it to make sure that is still Correct. It is.

In rechecking the load issue I noticed that up to my RPM limit there is no smoke, which is normal for this engine.

BUT...once I hit the limit she starts to make a small but distinct amount of WHITE SMOKE.

I took the air intake cover off and that gave me a small in increase in RPM.

The engine sure seems to be sucking a lot of air, but I have nothing to compare it to.

[perchance]

White smoke usually indicates incomplete combustion and could be caused by a timing issue.

[bstreep]

Even without the turbo, this engine will rev to 2800 rpms +/- in neutral (no load). We have the same engine, and had no working turbo last summer. Your turbo SHOULD spin VERY freely. You should be able to spin it and it should stay spinning for a few seconds. They spin at something like 70 or 80,000 rpms.

I thought black smoke was incomplete combustion? White is usually steam. Water from some where. How does the oil look? Black (normal), or milky?

BTW, I'm also thinking it's a fuel supply problem.

[Charlie]

I did a little research on the web and this is what I came up with. It applies to a gas engine but some are also for diesel's.

Engine Won't Reach Operating RPM. Check

1. Fuel condition. Type and Octane possibly old fuel
2. Propeller pitch or diameter, damaged blades
3. Restricted fuel pickup tube or anti siphon valve Fuel System Test
4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
5. Marine growth on hull and outdrive
6. Wrong gear ratio in outdrive
7. Restricted carburetor air intake (clogged flame arrestor)
8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
9. Poor cylinder compression Compression Test
10. Carburetor defective, or wrong type.
11. Fuel pump pressure and vacuum
12. Boat overloaded, improperly loaded, or improperly trimmed.
13. Engine Overheating
14. Engine timing and ignition system operation
15. Remote control cables and linkage for proper travel to open throttle plates fully.

Sorry I can't be of more help but my knowledge is limited.

[hpeer]

Thanks for all the info guys.

Mechanic is making noises that the next logical thing to do is to have the fuel injection pump serviced. That's gonna cost in both money and time.

Not criticizing the gentleman, he is probably right.

Pull pump on Thurs.
Send to Halifax Friday.
Get back Wed. If very lucky!

They look like $2k for a new one, if it comes to that.

[bstreep]

You might also try contacting forum member "Chief Engineer". He does consulting over the phone, and he's very likely to save you a ton of money.

[Charlie]

I would try the fuel bypass first b/c it is really cheap to try. Also looking at the troubleshooting guide the governor is also a culprit for low rpms

[hpeer]

I bite the bullet and sent the injection pump off to Halifax for service. I went back through the fuel delivery system, again, this am and found nothing amiss.

Removing the mixing elbow did nothing of significance, so can't be back pressure.

I feel hopeful, if not confident that this will resolve the issue.

My plan I to head to Greenland, and I anticipate a lot of motoring through Inside leads there so having confidence in the engine is important.

I Will try to report on what I find. Will be next week for sure.

[Charlie]

Good luck I hope that the injection pump resolves your problems.

[hpeer]

Repair shop says the injector oump is fit as a fiddle, not the problem.

Now I'm really stumped.

Have reached out to Chief Engineer and am trying to contact help at Mack Boring.

[Charlie]

The manual says to check for an adequate fuel supply (see test above) and that the governor may not be operating correctly (see manual). There is a spring in the governor that, if broken, would prevent it from supplying adequate fuel/

[triton274]

I am by no means a diesel mechanic, but have you checked the air filter? Perhaps it is partially blocked up?

[mikefp60]

I have 4JH3-TEs in my cat. Also did the Yanmar school a couple of months ago. Discussed low revs extensively. The wishbone chart for debugging low revs is rather complex. I guess the bottom line is that there are many different causes for low revs. I have one engine that will not rev up to the other no matter what I have done.

I can send you a shot of the chart or the whole service manual if you would like. Let me know.

Regards,

Mike
S/V Vivo