Engine wont rev after rebuild


#1

I have a 2006 Nissan Xterra SE turbo charged diesel. This is not an AMerican car, it is made in Brazil. I live in Costa Rica. Here’s the problem: After a radiator hose leaked and the engine overheated, I had to have the engine rebuilt. They put in a new head gasket, rebuilt the clutch, then they put it all back together and the car wouldn’t start. They took it back out, rebuilt the fuel injector motor, and installed all new injectors. When they put the engine back in the car, now it will start but it will not rev. It only idles. The mechanic has no clue what to do at this point. They’ve talked to the dealer and also to Bosch people (who rebuilt the injector motor) but everyone is pointing fingers at each other and nothing is getting done. I have a feeling it is something stupid, like a computer needs to be reset, but I really don’t know. Does anyone have any ideas? We’re going on 6 months now…


#2

Totally unfamiliar with your car but a new head gasket and clutch does not constitute a rebuilt engine, You don’t have an ignition system so that leaves compression, fuel and timing, You obviously have enough compression and timing for it to run, so you are left with fuel. Take the fuel cap off and change the fuel filter. If no change, you have to look at the pump or what controls the pump Is it a mechanical linkage to the pump or electrical? If electrical. is it controlled by a sensor or a sensor through te computer?
When the truck is idiling, does the fuel pressure out of the pump rise when you open the throttle? Find out what the pressures coming from the pump should be.


#3

I too am totally unfamiliar with this engine, but have they rechecked the valve timing?


#4

Have them check the fuel control rack on the injector pump.

The rack is what controls the amount of fuel supplied to the injectors.

Tester


#5

I am not familiar with this model but the first thing that sticks out is referring to a head gasket job as a rebuilt engine. That is not anywhere close to a rebuild and there’s also the issue of an overheated diesel engine which now be suffering compression problems.

As to not revving, my guess is an electronic throttle fault if so equipped or the injection pump timing is nowhere close to where it should be.

Considering the overheating, I’d recommend a compression test and determine whether the vehicle has much of a future. I doubt very seriously the problem is with Bosch.


#6

OK sorry I’m a girl, head gasket to me sounds like a rebuild but what do I know? I have been forwarding all your comments to the mechanic, thanks guys! I will let you know what it turns out to be.


#7

How bad was the overheat event? Did you drive it until it just stopped? A smoking, steaming mess? If so, you don’t “rebuild” those engines…You replace them with a new engine or a serviceable used one…A severe overheat in a diesel engine results to much damage to repair…

You can reset the computer by disconnecting the battery for a few minutes…Worth a try…Also, some diesels have an “emergency stop” throttle plate in the air inlet. If so equipped, it may need to be opened manually so the engine can breath again…


#8

I sent these comments to my mechanic, and he asked me to post this reply with quite a bit more info: Hi Linda. Thanks for passing on those comments. What you might tell those you are talking to is that this engine is not a Nissan design, it was designed and manufactured under license by a Brazilian company, MWM and was never, to my knowledge, imported into the US - it was used for vehicles sold outside the USA, only.

The engine is a strange and one-of-a-kind design. At the rear of the engine, between the flywheel and the block, under a cast iron cover, is a gear train of about five or six gears (not exactly sure of the count) which are driven off the crankshaft. These gears mechanically drive the camshaft and the fuel injection pump, among other things like drive the oil pump and engage the starter drive. The gear train must be exact for the engine to run. We never disassembled or even moved it; the gears were in exactly the same positions as they were when the car came in, when we reassembled the engine.

The timing of the camshaft-to-piston positions has been checked numerous times, by us and the dealer, and it is correct. We checked them and the Nissan dealer confirmed that they are correct - there are paint marks on the exposed portions of some of the gears where they checked them.

The fuel injector pump is 100% mechanical (manufactured by Bosch) and runs off the aforementioned gear train. We can only assume that the timing for the injector pump is also correct, since nothing in the gear train was moved, plus it was checked several times. That is also supported by the fact that the engine runs at idle but won’t accelerate.

With regard to the simple head gasket change, it was much, MUCH more than that. Because of the overheating the rings collapsed and damaged the cylinder walls. That necessitated doing a total rebuild with one new cylinder liner, all new pistons and rings, etc., as well as having the head planed and valves done. (New bearings, etc. also.)

Compression is now 400 PSI on all cylinders - higher than original specs. (I believe that factory specs are 350 PSI, but the exact number escapes me at the moment.)

The injectors are mechanical, are all new, factory fresh, and were made by Bosch.

A Bosch authorized rebuild facility rebuilt the injector pump. We (and the Nissan dealer) believe they somehow screwed up, but they won’t admit it. And that’s where the problem lies - getting them to come look at it and be forced to accept that the injector pump is the problem. They have tried to pass the buck to us, to the dealer, and to anyone or anything else they can think of as an excuse.

You know how Ticos are - they avoid confrontation - and I believe that the Bosch people are using that to avoid admitting their pump is the source of the problem. But nobody but this old Gringo wants to force the issue and get them to come out and either admit to the problem, or if that’s not it, to tell us what the hell the cause is. All I can say is that I’ll keep trying.

Feel free to pass this on to the folks on the forum, or where ever, and see if you can learn anything we don’t know.

Allen


#9

Check for restricted exhaust.


#10

if you are 99% sure it is fuel pump issue than replace it. you have spent $$$ already. if you replace pump and engine runs ok, than you can argue about the rebuilt pump


#11

High pressure injection pumps can be bench-tested easily enough…That’s what “Diesel Injection Labs” do for a living…There will also be a “lift pump” from the tank to feed the injection pump…


#12

This sounds like a fuel injection pump problem to me. That seems to be the least robust part of otherwise very robust diesel engines. It’s not uncommon at all for one to fail. If all the easy to do tests show no problem – compression is ok, fuel pump meets pressure and volume delivery spec, fuel tank and fuel lines are free of debris and water, fuel filter is new – I concur w/Caddyman above, have the injection pump bench tested.


#13

IF anyone is interested in seeing the guts of this weirdo engine, there are photos here: https://www.dropbox.com/sh/0o3sm86l81hv7xp/AAA0B1emOuFnhHRHtuAflHxva


#14

To achieve 400psi of compression requires either 28 to 1 compression ratio with zero leak down or a restricted exhaust… Just saying.


#15

this motor was obviously built in brazil. from the same crazy folks that like to play soccer. how old is the fuel in the tank? has this thing been sitting for awhile? maybe the fuel is contaminated


#16

The problem has been solved!!!

You might want to pass this info on to those on the forum who tried to help you, because the issue is quite unique!

With the gear train properly installed and the cover on, the engine was installed in the vehicle. Before the fuel injection pump can be installed, the engine has to be ‘set-up’ properly. To accomplish that there is a mark on the front pulley, also known as a vibration damper. (This pulley drives the belt which powers the A/C compressor and the alternator via a ribbed belt, and is commonly called a fan belt.)

The vibration damper itself is comprised of three parts: #1 is an internal cast iron piece which bolts directly to the engine crankshaft, #2 is an outer cast iron ring-like piece which does the actual driving of the belt. The two are joined together by #3, some compressed rubber, which serves to absorb any vibrations that may come off the crankshaft.

The outer ‘ring’ part of the damper has a critical timing mark on it which is made during manufacture. That timing mark is used to position (set up) all the engine’s parts, internal and external, including the fuel injection pump, so they are in proper relation to each other. Aligning that mark, the injection pump can be installed in the correct position to supply fuel to each cylinder at the proper time.

In the case of your engine, the outer part (ring) of the vibration damper had slipped (rotated) around the inner part and was about 30 degrees from where it should be, putting the timing mark 30 degrees off. There are no marks between the internal part of the damper and the outer parts, so the movement of the ring and its timing mark can’t readily be seen. In fact this vibration damper looks fully normal.

So, when the timing mark was (apparently) properly aligned, the internal parts of the engine, including the fuel injection pump drive gear, were out of position by a significant amount. When the pump was reinstalled using the prescribed method, although everything external to the engine APPEARED to be correct, it was not - the pump was about 30 degrees from where it should be. Therefore, the pump timing was close enough to allow the engine to run, but not to accelerate.

Now that we have found the problem it’s simply a case of reinstalling the engine (with the pump in the correct position), which will begin Monday.

I know it’s complicated, but I thought you’d like to know.

I think the car should be ready for pick up by the end of the week.


#17

U could crank motor to #1 @ tdc or whatever your spec is. Than check timing mark on dampener. Happens a lot on Chevy v8 motors.


#18

Thanks for letting us know that your problem was solved. You were unlucky it took so long, but very lucky that the mechanic would not give up. I can see where this would be a head scratcher to fix.