Odd idle

Dave 2000

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HDJ80 1994 Diesel Turbo Manual 182,000 miles (verified) full service history.

https://forum.ih8mud.com/80-series-tech/365673-my-lc-80-thread.html

I have had my 80 for about three weeks now and it is just perfect........until today! I was doing a three point turn on a road that was sloping and with a lot of camber, as I reversed and the back of the car dipped into the camber I noticed the revs dropped at idle from the normal rock steady 600 RPM down to about 400? So I pulled forward and as the car came to a stop on the other side of the road i.e. now pointing downwards the revs picked up to about 700 RPM.

Now the car has done this before but there were other factors involved making me dismiss it for example when turning and the power steering is loaded or the engine is cold ect but today the car/weather is warm.

Soooo now I am in diagnosis mode.

Car level idle perfect at 600
Car pointing uphill idle 400 and even lower depending on how steep the hill is.
Car pointing downhill and I have 700 rpm
Allow car to idle and let it roll downhill backwards and apply the brakes quite hard and the engine will cut out regardless of using foot brake or handbrake.
Drive along at a steady pace any speed you like put into neutral as the car starts to loose speed the revs rise very slightly and if I brake then the revs climb up even further.
I reversed down a very steep driveway and the engine was barely running at idle but rev it as much as you like and no problem. I switched it off and on the restart it struggled to catch, but it would rev real easy.

This is not a tacho fault i.e. the engine note is changing and of course the car is shuddering due to the low revs ect.

So I'm thinking fuel starvation, now my fuel gauge does not work but I know there is loads in the tank, the low fuel light is not on but I put another 20 litres in anyway and no change. TBH if you took the pick up pipe out of the tank the engine would run perfect for a minute or two until the fuel was depleted but this problem happens instantly the cars attitude in relation to being out of level. The fuel filter in the tank is clean, the fuel filter in the engine bay was changed 2000 miles ago and fuel injector cleaner was used when this was changed, the air filter is clean. If there was water in the filter which I have seen before in other cars this would not cause the engine to falter the instant the car was not level right?

I parked the car with the rear downhill and allowed it to idle at about 400 and went around the pipes around the pump and filter and no change whatsoever, I even crimped the fuel pipe between the filer and pump and it took about 30 or 40 seconds before the engine note changed as the pump was being starved, i released the crimp and the engine picked up straight away back to the 400 rpm's.

The car pulls like the proverbial train for testing purposes only :D I took it up to well, let's just say I MAY have exceeded the 120KPH or about 75MPH limit here but trust me the car was pulling hard and there are no issues when getting to this speed with the foot hard down.

And of all days today I had to pick up a load of paving slabs for a friend so the car was loaded up and the back was dipping down and sure enough the idle was just under the 600, pulled away and the car drove as though the weight was not there just perfect.

The car is still driving perfect this evening and of course if you are slowing down you do not notice the slight increase in revs unless your looking for it. It is not related to the brake lights loading the alternator, it is not related to the vacuum pump as it happens if I use the handbrake.

Is there a 'sump' inside the diesel pump that could have enough rubbish in to alter the idle when the car is tipped? The reason I ask is because the steeper the angle that the rear of the car is down the lower the revs and vice verse, and yet when level I can easily exceed national speed limits and it gets there without hanging around?

If you 'blip' the throttle at idle the engine responds straightaway, the throttle cable has enough slack in it to allow for the engine moving on it's mounts ect.

Tommorow I am going to connect a clean container of fuel direct to the pump and see if that makes any difference

I have been a mechanic for many years but mainly petrol with a fair bit of diesel stuff mixed in but I have not seen this before so any help would be appreciated and anything else I can try tommorow?

regards

Dave
 
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Not the 1st post on this issue of seemingly low fuel pressure when the fuel tank is lower than fuel pump.
Very soon someone will suggest you add an inline fuel pump.;)

IMO,you would be better off getting the pump looked at and try to determine the exact nature of the problem
There is a regulator valve that can be adjusted.It diverts excess fuel back to the tank,in your case it maybe allowing too much back at idle speeds.
I would also try turning the idle up a fraction,closer to 700.

Of course you are wondering why this is happening when it didnt happen before.
There was an owner in Haiti having exactly the same problem. I cannot recall his name or if it was fixed.
 

Dave 2000

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its normal for your 80 with the 1hd-t to idle at 650. It will kick up when your ac compressor turns on.

That's right, factory spec is 600 - 700 all that is normal but the idle changes speed relative to the vehicle not being level.

regards

Dave
 

Dave 2000

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Thanks for that Rosco, I will try and rule out anything to do with fuel flow today. I will run a tube from a container and bypass all the filters and plumbing ect and see how it goes.

regards

Dave
 

Dave 2000

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Very soon someone will suggest you add an inline fuel pump.;)

IMO,you would be better off getting the pump looked at and try to determine the exact nature of the problem
There is a regulator valve that can be adjusted.It diverts excess fuel back to the tank,in your case it maybe allowing too much back at idle speeds.
I would also try turning the idle up a fraction,closer to 700.

Of course you are wondering why this is happening when it didnt happen before.
There was an owner in Haiti having exactly the same problem. I cannot recall his name or if it was fixed.

I agree to not fitting an inline pump at the moment but you mention a regualtor valve? Whilst I understand the theory I do not understand why this would be affected by the vehicles attitude to the road unless my small 'sump' in the pump theory holds water? Could you describe where this valve is on the pump?

Thanks for your input on this,

regards

Dave
 
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I agree to not fitting an inline pump at the moment but you mention a regualtor valve? Whilst I understand the theory I do not understand why this would be affected by the vehicles attitude to the road unless my small 'sump' in the pump theory holds water? Could you describe where this valve is on the pump?

Thanks for your input on this,

regards

Dave

From my knowledge of the denso pump ,you tap it in,but I forget whether it increases or decreases the flow back to the tank.
You are supposed to measure the flow as you adjust it.
And when it been tapped too far in it is recommended to be replaced.

This is a Bosch VE which is fundamentally the same.NOTE the feed pump is actual arund the othe way so the main shaft goes through it
I got the info off an aussie site that was discussing the feed pump

YANMARVESmall2.GIF


I recommend you have a good read of the fuel section in the manual before you touch anything;)
 
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Dave 2000

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Thanks for that Rosco, I am about to head out to the garage and start to look for any clues. I have found one or two other threads on mud which mentioned low pressure at idle but I am unsure if this would affect the car so suddenly. It does make sense i.e. it is harder to pull fuel from the tank when the tank is lower however, even when idling with the front pointing even slightly uphill the idle is slower, release the brakes and as soon as the car starts to roll backwards the engine revs climb for a second and then the combination of the braking or the car rear dipping lower brings the revs straight down. I noticed that the adding of a pusher pump helped some people so I tried the following, I parked the car rear facing down hill and the idle at 400 rpm, I then pumped the primer on top of the fuel filter and it made no difference whatsoever to the idle despite giving positive pressure to the injection pump.

I will report back today and update the thread.

Thanks again

regards

Dave
 
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One other odd thing about your problem is that I have heard of it happening to maybe 3-4 HDJ8* but I have never heard of it happening to the non turbo 1HZ.

Looking forward to getting to the bottom of it
 

Dave 2000

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So an update is in order.

I adjusted the idle speed just in case the rev counter was showing 600 when I was perhaps only running at 500, no difference even when idling at 800 rpm.

I removed the fuel banjo where it enters the pump and was thinking there may be a filter there, no filter and all appears clean.

Replaced the fuel filter despite it's low mileage, I only had a 'mickey mouse' copy filter which I fitted and will pick up the OEM on Tuesday next week. I drained the old filter and there was a brown 'scum' lke pieces floating inside, it looked like brown ash floating in the fuel, I felt it with my fingers and it is not solid. I checked the fuel lines were clear and blew them through anyway, put it back together no change.

I then disconnected the fuel line from the feed pipe and immersed it in a clean container of fuel no difference, so I filled a long pipe up with fuel and with the pipe vertical no change the idle still drops when the rear is lower than the front, this adds to my earlier observations that using the manual pump did not help idle.

So unless anyone else has any ideas I am stumped, it does not interfere with every day driving and by turning the idle up has not changed anything. It has been suggested that the injection pump has a problem which I can accept but what can be wrong with a pump that will not run properly when taking out of the horizontal plane?

I have put some more injector cleaner in and will keep the tank with a strong mix of this stuff for awhile, I do not suspect injectors but it may help the pump if there is dirt in there?

I have just had a thought..........could it be the stop plunger moving back and forth? I am trying to think of what can stall the car and no fuel is in thinking with the stop valve, I know it's a long shot but straws and grasping are coming to mind. FWIW I took the car up the motorway a few minutes ago during the 'siesta' when everyone is asleep including the police, 110MPH no problem and gets there with no delays, no smoke, smoothly and the car drives perfect ect.

regards

Dave
 
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Dave 2000

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Further to my last post I have removed the stop solenoid, found the mesh filter, all was sparkling clean, flushed through with a few pumps on the primer just in case, put it all back together and..........no change!!

regards

Dave
 
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So unless anyone else has any ideas I am stumped, it does not interfere with every day driving and by turning the idle up has not changed anything. It has been suggested that the injection pump has a problem which I can accept but what can be wrong with a pump that will not run properly when taking out of the horizontal plane?



Dave

It maybe in the govenor.Weak governor spring or idle spring.
 

Dave 2000

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It maybe in the govenor.Weak governor spring or idle spring.

Thanks for the reply. Why would the governor or spring cause the idle to alter simply by altering the attitude of the car? I can jack up the front or put bricks in the back and the revs drop accordingly. If the car is level it would idle at 600 rpm all day without falter up or down.

regards

Dave
 
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Thanks for the reply. Why would the governor or spring cause the idle to alter simply by altering the attitude of the car? I can jack up the front or put bricks in the back and the revs drop accordingly. If the car is level it would idle at 600 rpm all day without falter up or down.

regards

Dave

I was wondering if the spring was sloppy enough to allow the tension lever to fall back and alter the fuel supply.
Something inside the pump must be causing the fuel flow to change.
The difference in the amount of fuel it needs at idle between 600 and 400 rpm must be minute
 

Dave 2000

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I was wondering if the spring was sloppy enough to allow the tension lever to fall back and alter the fuel supply.
Something inside the pump must be causing the fuel flow to change.
The difference in the amount of fuel it needs at idle between 600 and 400 rpm must be minute

I know there is no play on any of the external linkages but the sensitivity of this is incredible, even on a gentle slope pointing up the release of the handbrake and the initial movement backwards will give the rise in idle speed and then a touch of the brakes and the revs quickly sink. I have been told by three UK diesel owners that it is very common and will not affect the life of the pump. Some have fitted the secondary feed or 'lift' pump which seems to help, I have contacted a diesel guy in the UK to see what he thinks.

Thanks for the input,

regards

Dave
 

Dave 2000

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So another update, I replaced the 'mickey mouse' fuel filter with a genuine Toyota item today and again no change, of some interest is the OE filter has LESS flitering medium in it than the copy?

I have spoken to a diesel guy in the UK and he said he has not seen this idle problem before other than when filters are blocked and this problem was always connected with the inability of the car to reach any decent speeds ect so that is a dead end for my problem at the moment.

Watch this space.............

regards

Dave
 
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As I mentioned before,its odd it only happens with turbo models. Whatever the difference is between the 1HZ and 1HD T pumps maybe the key.

I still have a hunch it is something internal and to do with the governor springs ,but only a strip down would resolve that.

Interesting video

 

Dave 2000

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I agree, with all the testing and clean filters ect that looks to be the issue. The fact that the governor arm is like a pendelum but standing instead of hanging and is sensitive to movement fore and aft points it in the right direction.

I will start reading the FSM because I do not like putting my car in a workshop so will do the studying and see if I can do it myself when I have the time, the video is great and I have seen one or two others on you tube as well thanks again Rosco.

regards

Dave
 
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Although I can't offer any further advice my 1hd-t has done this for a few years and like yourself I came to a dead end with the diagnosis. It hasn't got any worse though my idle never gets low enough to stall so I just live with it. Must be easily over 3 years and 50k miles since the problem started with no other ill effects. :)

Jamie
 

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