92 HDJ81 jerk at highway speed

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Hi ,
l am puzzled,l have a customer's HDJ81 with auto tranny here,it drives normal under 80 km/h,at over 90 or 100km/h,it will jerk for half a second every2 to 3 minutes,l can't differentiate if it is engine or transmission,anybody have experience this?
TIA
Simon Liew
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Simon, I have heard about similar things with the Zexel IPs in the Patrol which is pretty much the same as the Denso IP in the 81s.

In one case the culprit was a clogged strainer screen which is under the the inlet banjo fitting on the IP. It would only manifest itself at highway speeds. I am not sure why only highway speed, but once it was cleaned, the issue was solved. If I remember from previous posts about the Denso IP, it has the same strainer under the inlet banjo fitting.

Other causes of jerking like this have been a defective TPS or transmission computer. I am sure your FSM has a procedure for checking these. If not, I can check through my FSM and see what the procedure is.
 

PacToy

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its sudden almost like if your driving a manual and hit the clutch for a split second and then back to normal until it happens again.

My HJ47 will do this once in a while on the highway. Just driving along and then the engine comes off step, then comes back on step like nothing happened.

Just for a brief sec or two, right?
 
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Hi,
l am working on the truck,truck belongs to WAF450,feel free to chime in Wayne.
Rich and Randy,it is a sudden jerk like a misfire of a gas engine under load,but only for half a second,that is why it is so hard to find what is wrong.
Simon
 
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A few thoughts...

Has the ACSD been removed yet? Perhaps a part from that nasty little device has fallen into the pump.

Are the splines on the birfs/driveplates okay?

Birf broken?

Sounds like a slipping spline, or something. Need to determine if it's an engine problem or a trans/transfer/axle problem.

Loose caliper?

The list could be endless....

Grabbing parking brake shoe that is loose...



~John
just tossing ideas out there.
 
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The splines on the front were just replaced, also the CDL will not engage. I tested the switch and relay were good but haven't looked at the acuator. CDL stopped working just prior to replacing the splines on the front. As around 1 1/2 months ago, the truck would be in drive "didn't matter which gear" then pop to neutral on the fly. its not the linkage on the shifter as it changes gears goods but was letting go. Replacing the splines and bushings etc in the front resolved the problem. But know it jerks on the highway its weird. AVM hubs are on the front, and "power rod" install done. Thanks for the help guys i appreciate it.
 
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PacToy

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yup like 1 second or so. Im hoping its the screen in the IP:bang:

Yeah, yeah, just driving along and the truck just goes dead but come right back alive, right? Just enough to scare the wits out of ya the first time it happens.

Is your 91 81 a manual or auto?

Hi,
l am working on the truck,truck belongs to WAF450,feel free to chime in Wayne.
Rich and Randy,it is a sudden jerk like a misfire of a gas engine under load,but only for half a second,that is why it is so hard to find what is wrong.
Simon

I was having Chris (lynchmob) do my H55 and 12H-T install on my 78 40 and while I was on the phone with Chris, I asked him the same question about my HJ47 doing the same. He said: It sounds like a ground is coming lose somehwere.

Food for thought.
 

rchalmers3

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....... also the CDL will not engage. CDL stopped working just prior to replacing the splines on the front. As around 1 1/2 months ago, the truck would be in drive "didn't matter which gear" then pop to neutral on the fly. its not the linkage on the shifter as it changes gears goods but was letting go. Replacing the splines and bushings etc in the front resolved the problem. But know it jerks on the highway its weird. AVM hubs are on the front, and "power rod" install done. Thanks for the help guys i appreciate it.

Man, I dunno, but I'll bet you my entire sandwich (bacon w/cucumber on wholewheat toast) its an unusual drivetrain (tranny) problem. I can't imagine that if fuel is cut at that speed that the power loss would feel so abrupt.

Have you considered rigging a test switch on your fuel stop circuit to test the fuel interruption theory? If you could operate the vehicle at speed and shut off the fuel at will, you could decide if the idea of fuel starvation due to a plugged screen or if any interruption to the fuel solenoid could be a potential cause.

Just thinking aloud here.....

Rick
 
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Hi Guys,
took the banjo off the fuel inlet,there is no screen there.,look at another 81 ,no screen too.
it is a very slight jerk at 90km/h and up,it will not do it at 80k,only for half a second,it is hard to diagnose problem like this at speed,anybody else have simlar problems like this??
 

Dave 2000

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The later 94 IP has a screen NOT under the banjo but under the fuel inlet stop plunger so check there.

Another thought springs to mind, it could be a small pinhole in a fuel pipe or in the rubber primer diaphram, this brings in air at a predetermined rate and causes a misfire as it passes through the pump/injectors. The fact that it only happens at speed would indicate it is when the fuel system is under high demand/flow.

Have you tried speeding up and seeing if the problem cycles faster? The tank filter may need cleaning ect. You can put a CLEAN container of diesel on the floor of the passenger side and run a CLEAN pipe straight to the pump. Unused fuel will be returned to the main tank so you will not have long to complete your tests but it will eliminate the tank/filter head/piping ect.

BTDT trying to sort out this problem: https://forum.ih8mud.com/diesel-tech-24-volts-systems/371858-odd-idle.html


regards

Dave
 

arnott1t

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I had this exact thing happen in my HJ in -40C weather on a trip home. Thought it was fuel gelling but ended up being my EDIC. I know this unit doesn't have that but there must be some other type of fuel shut off. Could it be acting up? Once I unhooked my EDIC rod I cruised home happily ever after.
 
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its now doing it around 55 kph once in awhile and it seems like the faster you go the more often it happens. im supposed to take it to a tranny shop this week and see what they say,as simon's very busy and probably wont have time to do all this testing. im getting a job with local power authorities which involves me to do a lot of highway travelling and i dont have the time to be playing around with the 80. It would be a shame to get rid of it after doing so much work to it.
 
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