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Idle rpm

Gizmops

Active Member
Joined
Jul 3, 2022
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spain
Morning all. My idle rpm from cold is about 600 but rises to 925 when warmed up, I thought it was a hand throttle fault, stripped that yesterday, apart from a faulty knob iis fine. Seen to have sufficient free play at pump for normal throttle. Any clues please. It doesn't feel right selecting drive at 925rpm.
 
Normally the problem is the other way round if the cold start advance is playing up...
What engine do you have ?
Petrol ? or diesel ? and what engine model ?
 
Hello Gtimbo, I have a 1992 4.2 turbo diesel auto 1 hdt engine
 
Try getting the engine warm so the idle is high then disconnect the throttle linkage at the injector pump ...if the high idle stays the same and the leaver is against the throttle stop then it's most likely an internal pump fault with the cold start advance .
Did this happen suddenly ?
 
Hi yes I think it did suddenly happen, I cantv remember when, just getting annoyed with it.
 
Just for info, engine starts at slightest turn of the key both from cold or hot, no visible leaks externally, no smoke, no misfires. Only had her 9 months so have-nots previous history. 260kms on speedo



7.
 
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Do some basics.....
Change the fuel filter and check for air ingress in any of the fuel lines.....
Take a picture of the FIP and post it so we can see exactly what pump you have and what's fitted ....
 
The truck in the garage with a power steering leak at the moment so can't take photo of the pump, I will post as soon as I can. Thanks
 
Hi, attached is a photo of the pump, power steering pump sorted, a few seals replaced, pump reported as good.
 

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Did you fit the non return valve in the FIP return line ?
If not that suggests a previous owner was having a problem with fuel supply.....
My first thing to do would be supply the FIP from a can that's higher than the FIP ....be scrupulously clean and supply fuel straight to the pump..... then warm the engine up and see what happens to your idle rpm , if it's then stable you know the problem is in the fuel supply.... the steel pipes from the tanks can get very small holes in them and the hand primer on the fuel filter housing can let air in ...
 
Hi Grimbo, no the non return valve was already fitted when I bought her. I have changed the fuel filter, I have checked fuel line to tank, no sign of any weepage so don't know how air can get in, I will get some more fuel pipe and try it well higher than fip inlet, and also check hand primer when I can find it. Thanks
 
Found the hand primer pump on top of filter, no weepage, what next please.
 
You need to prove if the problem is the pump or in the supply to the pump.... try running the engine with a fuel supply from a clean can straight to the inlet of the fuel injection pump and make sure the can is higher than the pump.... see if the problem is still happening .

If it is then the fault is 99% likely to be the pump

If the problem goes away then next move is to have your fuel can at the same height as the fuel tank.... so lower than the fuel pump but still connected straight to the pump missing out the filter head etc.... what happens now ? do you still not have a problem ? if so then the small internal lift pump part of the fuel injection pump is working OK ....some people fit an inline electric pusher pump to help with fuel supply as the pumps get slightly worn .

Next step is still with your fuel can supplying fuel connect it to the tank side of the filter.... what happens now ? is it still running fine or has the problem returned ? The filter head and hand primer can allow air to be sucked in without leaking fuel......

Last stage is to run a rubber fuel line temporarily from the fuel pickup on the tank to the fuel filter and see what happens....has the problem gone away ? if so then the problem is in the metal lines from the tank pickup to the filter....

Also remove the fuel pick up from the fuel tank ( you have to remove 2nd row seats and fold the carpet back , then remove a small cover to be able to remove the pickup from the top of the tank ) you will find a small filter on the end of the pickup in the tank......these can get blocked so it's worth doing anyway .
I know that's a lot of messing about and several goes at bleeding the fuel system but it's the only way to isolate the part causing your problem

Too me it's suspicious that the previous owner fitted the non return valve.... this was done to overcome a problem .
Also it's worth checking the condition of the rubber fuel hoses and tightness of hose clamps ...the " jubilee " type hose clamps are not always good for smaller diameter hose and the fuel line of petrol hose type clamps are often better .
 
Thanks Grimbo, great information, not sure when i can make enough time to follow all the stages but will make a start getting the corrrct size rubber pipe and get rid of the non return valve.
 
Hi ,
It looks your Ascd has had the speed adjustment arms removed, I think some one has set the idle to allow it to start and run but it’s not correct for when it’s warm?
I don’t think you have an air problem as they just don’t start until primed up, it would be hunting etc and maybe cut out.
 
What is the ASCD, can anybody post photos of what is missing, am I going to have to take her toToyota
For a fix. Hope they say the fip needs replacing.
 
The ascd is a wax stat that advances the diesel pump for cold starts, this slowly retards the timing as the engine temp warms.
You just have the threaded spindle showing with no arms or springs on.
The ascd can be removed and a blanking plate fitted.
I have removed mine for the last couple of years and it’s fine, I just use the hand throttle if it’s really cold to up the idle speed.
 
I have attached two pictures, one with ascd fitted and one with the blanking plate.
 

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