1HZ N/A running inconsistent. (1 Viewer)

[Tinman]

Background.
1991 HZJ75 N/A
Injector pump and injectors rebuilt about 4 years ago 50000klm. Was much better after that but have never been 100% happy with it. Have had the vehicle for 33 years and use to to a boat regularly with it.

Currently it runs inconsistent. Sometimes it runs good and then the next day it struggles up the hills and puff black smoke and other times it feels like it leans out and wont rev past 3000rpm. Fuel economy goes bad and get up to 100 klm less out of a tank. Sometimes it is like it has a dead spot. Lift my foot and ease it back on it runs better.

450000klm
Compression is good
Valve clearances all good.
Pump timing ive checked 3 times as well as trying advanceing and retarding it slightly. Runs best where it is 1.06
Tank breathers are clear.
Filters in tanks have been replaced.
It was getting some air into the fuel lines but i have now eliminated that and pressure tested the line’s between the injector pump and fuel tanks including the pick ups.

Is there some sort of advance mechanism in the govenor that could be playing up.?

What else could cause this.?

Could this be an injector issue?

Thanks in advance for any advice.

 

[bj70bc]

i would use a clear fuel hose to visually inspect for air while running....
injectors is always a good thing to do
has the head ever been re+ re'd

 

[Tinman]

i would use a clear fuel hose to visually inspect for air while running....
injectors is always a good thing to do
has the head ever been re+ re'd

Heads never been off and compression readings are all good within 10psi.

 

[snapdragon]

Check for pinhole leaks in the fuel line.

 

[sodafeld1]

Losing any engine oil? Any obvious leaks ? (not meaning to be a smarty pants) Maybe move it to the diesel section

 

[Rigster]

Since you have ruled out air in the lines, this seems to me like something in the fuel pump being inconsistent as you say. You do not state whether you have replaced the fuel filter under the hood. Does this pump have an altitude compensator? It will look like a boost compensator on top of the pump. I wonder if it could be acting up, as that could create irregular fuel control.

How much do you trust the shop that did the pump and injectors? Do they have a good rep? Lots of experience? If so, you could take it back to them, as 50,000km is nothing for new injectors and pump. Could be they also might know what it could be.

 

[Tinman]

Since you have ruled out air in the lines, this seems to me like something in the fuel pump being inconsistent as you say. You do not state whether you have replaced the fuel filter under the hood. Does this pump have an altitude compensator? It will look like a boost compensator on top of the pump. I wonder if it could be acting up, as that could create irregular fuel control.

How much do you trust the shop that did the pump and injectors? Do they have a good rep? Lots of experience? If so, you could take it back to them, as 50,000km is nothing for new injectors and pump. Could be they also might know what it could be.

Fuel filter is good. There is no altitude compensator on it. No turbo boost.

The other thought that rolls through my head it could there be a tiny bit of rubber off an o ring floating around in there somewhere?

I know there is some pretty knowledgeable people on this site, so hopefully someone can point me in the right direction before I spend money getting it ripped apart.

 

[TreadingLight]

Use a clear line to definitively rule out air.

But consider also the air ingress could be intermittent.

I had a diesel that was misbehaving similarly and it turned out to be a hairline crack in a hard-line along the frame.

Only failed when twisted just right to open the crack.

 

[Tinman]

Use a clear line to definitively rule out air.

But consider also the air ingress could be intermittent.

I had a diesel that was misbehaving similarly and it turned out to be a hairline crack in a hard-line along the frame.

Only failed when twisted just right to open the crack.

I did consider that one of the hard lines may have been damaged. Stone from all the gravel roads That is why i pressure tested it all.

 

[sodafeld1]

Struggle uphill makes me think fuel, if not lines or a leak maybe bad fuel, bit of water could make it through filters perhaps.
Black smoke makes me think oil burning or incomplete combustion pending on smell.
50k on injectors and pump should be good for a long time more.

Don't think the hz pump has a leather diaphragm, so not that.

Wonder if bad fuel coked your injectors? Also wonder how your manifolds are? Sounds like you have done some thorough hunting. Again not trying to be smarty pants, but if the engine is squeaky cleaned, then driven , can anything like leaks or carbon be observed? Intake manifold, coked injectors or pump would not be able to observe anything. Give it a dose of lubrimoly diesel purge? If that helps, then likely it's your injectors.

 

[TreadingLight]

I did consider that one of the hard lines may have been damaged. Stone from all the gravel roads That is why i pressure tested it all.

I still think it would be worth it to check visually with a clear line while it is misbehaving. Verify your pressure test results.

 

[Squash]

Use the clear fuel line. You will never see a leak because the system in under vacuum.
You can leave the clear hose between the IP and filter for quite some time. Just carry a spare hose or length of clear hose.
You can also go IP to the hard line if you suspect the filter.
Don't be afraid to try a ride by bypassing your fuel lines using clear hose, a container and fresh fuel.