1hdt miss in low revs, diagnostic help please. (1 Viewer)

[Zoeteke]

Hey guys, need some help here. Bought a ,93 HDJ81 cruiser which has developed a slight flutter or noticeable miss in the lower revs. Goes away at around 1800-2000 rpms. Have had a heap of work done attemping to isolate and remedy but still the miss remains. Done so far......
All injectors done, new nozzles etc, pump pulled off and new driveshaft, transfer pump, d valves, d/v springs etc. all done by reputable diesel and turbo crowd that come highly recommended. Compression test done came back ok so they suspect tight valves....the miss remains and it still goes away after 1800-2000rpms.
1000 kms after getting truck back the pump drive comes off resulting in bent valves, broken cam, stuffed head. Apparently the locking tabs were never bent over to secure the bolts. Back to mechanics who immediately took full responsibility without any issues. While the head was off I got them to pull the Pistons and put in a new set of hoops and big end bearings. They footed the bill for all work on top including a refreshed head, guides done, valves done, new cam, belt tensioner etc. all back together and still the frigging miss remains. Suspecting the injectors again I pulled them myself and sent them to a reputable fuel injection specialist for piece of mind. He found a variation of 15 bar between the respective pressures and went right through them setting them all to spec so I could definately eliminate them as the cause of my miss. Put them back in but still the miss is there. So....... Not the injectors, not tight valves, not rings or Pistons (compressions all good although new rings still need to bed in more) who's got some clues???....back to the injector pump perhaps?

Incidentally......went for a drive the other day, bloody gutless struggling to get up a very minor rise. On the driveway. All good once I got enough revs and the turbo kicked in and it then drove well....until i had to stop at any intersections. Then again, very, very gutless until the revs picked up a little and the turbo kicked in. Very scary struggling through an intersection with the boat behind. Read the forums and found a thread stating same symptoms caused by faulty diode in alternator??? Maybe some relation between alternator output at idle and low revs??? Anyhow, knowing I had a battery on the way out, I replaced both batteries with new ones and the gutless symptom disappeared? I have no idea if this could be related to my miss but perhaps one of you knowledgable chaps may note some significance?

 

[B Point]

Is it an actual miss or just a flutter during acceleration? I have something similar but can't tell if it's an engine issue or something in the driveline. It's kind of like when you pull up beside another truck and the exhaust sound wave frequency from both trucks interact. It's like a ...wha, wha, wha,wha, wha...sound vibration. It could be an artifact from the 3 inch exhaust system. It's pretty throaty on acceleration. I also suspect a possible front driveshaft vibration.. I should pull it one day to see.

Or maybe it's all just me being weird and paranoid.

 

[Zoeteke]

Mine is definately a miss, easily felt and heard. I'm going to try the clear fuel line to look for bubbles etc. smooth as after 1800-2000 rpms.

 

[roscoFJ73]

If they had the fuel pump off, did they bench test it? Any problems with a fuel pump would be replicated when bench testing , either way you would know whether its fuel related or not.
If it hasn't been done ,it needs to be and probably should have been the 1st thing to have been looked at.

EDIT, When you mentioned compression , was that from the pump or the engine?

At least your mechanic is to be commended for rectifying his error.

Its hard to see how it would be an electrical problem with an engine that fires from compression.
Air entering fuel lines usually happens overnight and causes hard starts and goes away as the engine turns faster. Air problems tend to get worse over time.
But its worth checking just to say its been done.

Auto transmissions also give that gutless feeling if out of adjustment. I forget the name of bit that causes it , but it has to do with the shifting mechanism.

 

[Zoeteke]

Hi, thanks for the input. Yes as far as I know the bench tested the pump and weren't entirely happy with it and wanted me to try and source another pump. Unfortunately the one I sourced was not entirely compatible and was pretty poor condition anyway they said. So in order to get me going again they replaced any suspect parts they could in the original pump but obviously not the housing. It was after this I had the drive gear come away resulting in the subsequent head replacement and rings and bearings. This was all nearly 12 months ago and financial circumstances resulted in my parking it up until just recently when I could again focus on getting it right. I plan to go back to the diesel mechanics one last time to see if they can eliminate the miss down low. I would imagine they will say that it's best to source a new or good replacement pump/housing and focus on getting the pump A1. Trouble is they are so bloody expensive here in NZ and not that easy to find someone willing to split from a good engine at the dismantelers.

I've temporarily fitted clear fuel line to look for air and no bubbles.

As far as the intermittent gutless issue goes I'm thinking along the same lines as you. Hard to see it being something electrical to do with the engine when it's a diesel, especially so with a mechanical pump. When it does happen, If I select low ratio it's fine, shift back to high and it's again fine so perhaps a trans issue has surfaced while the truck was sitting idle. I understand the A442f has a few solinoids in there so wondering if there is a sticky one. The trans has had a service a couple of thousand kms before it was parked up and was going well previously.

To summarise, I think I have two separate issues. The first being the miss which may possibly be the pump as injectors are fine and compressions and valves are also good.
The second issue of intermitant gutless ness until the turbo starts working may possibly be to do with the trans? More than likely just coincidence that it came right at the same time I replaced my batteries as it has returned on a few occasions since and has again come right when selecting low ratio and then going back into high. And again coincidence I found that thread where a chap had the same issue which apparently went away after replacing his alternator. I figure nothing to do with alternator output at idle as I'm getting 14.36 volts output at idle.

I'll go back and see my mechanic and decide on the best approach moving forward, in the meantime I will try to find a good pump or another housing to suit my engine. Get the miss sorted then the trans. Will keep you all posted.

 

[roscoFJ73]

I would try and find another mechanic because anyone who knows diesels will tell you tell you that if the pump can not supply fuel at the required pressure it will not run correctly.
I know its not cheap(from experience) but the only way to fix a bad pump is to replace ALL the worn parts. I think the housing cost me $500 9 years ago for a 1HZ.
if the housing is no good , it is probably flogged out around the timer piston. Common problem on Denso rotary pumps(maybe on all rotary pumps). Im overseas at the moment and don't have access to my pics on my home computer

 

[Catchsash]

Zoeteke,

Very well documented issue, facing a similar issue, I am eager to know you managed to solve the problem and what was it in the end???

 

[JoeiPH]

i have the same problem right now.
we replaced the whole pump with a new one. new nozzle.
i have a 3" exhaust. the idle shake is noticeable kn the start up. but goes away when the engine revs above 2000.. someone adviced me to change the tupe of oil called caltex DELO gold. i havent done it yet. let see..

 

[roscoFJ73]

Good luck with that but Ill believe it when I see it.

 

[BCR4619]

when you start it up and it stumbles, prime the fuel filter pump by hand and see if it goes away, you may be getting air in the system somewhere.

 

[JoeiPH]

fixed... bought a new injection pump.. bench tested.. replaced new injection nozzle... just a little adjustment on the idle.. the shop did the pump but left idle at 400 rpm. i adjusted it to 600.. works well now.
my old pump has been rebuilt twice already..
still needs a change oil though. hahaha.

 

[Madcrix12]

fixed... bought a new injection pump.. bench tested.. replaced new injection nozzle... just a little adjustment on the idle.. the shop did the pump but left idle at 400 rpm. i adjusted it to 600.. works well now.
my old pump has been rebuilt twice already..
still needs a change oil though. hahaha.

where did you get a new pump?

 

[roscoFJ73]

Joe hasnt been here for 2 years. You need to get the figures on the side of the pump and start searching online for the best price. Japan and the Middle East are usually the best , and Partsouq in france.
There is a Toyota and Denso part number. There is also the 3 number one in big numbers shown here, most injection shops want this number talking on the phone.
This a 1HD T pump, the Toyota part number maybe the same as yours.

 

[roscoFJ73]

About $4300USD here Pump Assy, Injection Or Supply

The problem with some of these online suppliers is they sometimes dont have the part , but they dont tell you before you have ordered and paid, then you wait for a refund. So ask them first.