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Low Starting Fuel Pressure
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Posted 10/18/2021 10:41 AM
colsG55
Veteran


Date registered: Aug 2013
Location: Dubai
Vehicle(s): G55 Classic 2000, TD5 110, 200 Series Land Cruiser
Posts: 209
100
Low Starting Fuel Pressure

G’Day all,

Ref 1999 G55.

I am having trouble starting especially when the engine is warm. Most of the time is is able to start OK with a small delay but if it fails to start straight away the fuel pressure seems to drop and it sometimes wont start without leaving it for quite sometime until it cools right down and fires up. It has always been a bit of a cranky hot starter.

When you turn on the ignition the fuel pump does not run, when you bleed some fuel out of the front of the fuel rail on the engine there is some pressure but it seems quite low and no where near as much as when the engine is running. As soon as the engine starts the fuel pump is working as per normal.

I seem to recall prior to this issue the fuel pump use to run for around 10 sec when the ignition was first turned on then either times out or possibly there maybe a fuel pressure sensor in the system which shuts off the pump until the engine runs.

So far I have replaced the fuel filter, fuel pump and swapped in a spare K40 relay all to no avail with the same results.

I checked all the fuses below the dash and on the K40 and they are all OK, the 15A K6 fuse on the K40 was blown, but I don’t think this relates to the fuel pump but the air pump, it has also been replaced with no change.

Does anyone know of a relay which maybe the cause or if there is a fuel pressure sensor in the system when might be sensing high pressure and inhibiting the pump prior to engine start.

Any info or previous experience with a similar issue should be appreciated. I have searched the old topics but nothing seems to directly relate.
#243071
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Author
Posted 10/19/2021 5:31 AM
colsG55
Veteran


Date registered: Aug 2013
Location: Dubai
Vehicle(s): G55 Classic 2000, TD5 110, 200 Series Land Cruiser
Posts: 209
100
Re: Low Starting Fuel Pressure

It started much better when the engine was hot today, the new pump and filter might have done the trick.

Time will tell.
#243076 - in reply to #243071
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Posted 10/19/2021 12:45 PM
J.R.
Elite Veteran




Date registered: Apr 2006
Location: Southern Maryland
Vehicle(s): 00 G500, 09 911 4S, 11 Cayenne S, 86 280GE (sold)
Posts: 828
500
Re: Low Starting Fuel Pressure

crank position sensor would be on a short list for me: http://www.pointedthree.com/disc/forums/showthread.asp?tid=19795&po...
#243077 - in reply to #243071
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Author
Posted 10/20/2021 4:25 AM
colsG55
Veteran


Date registered: Aug 2013
Location: Dubai
Vehicle(s): G55 Classic 2000, TD5 110, 200 Series Land Cruiser
Posts: 209
100
Re: Low Starting Fuel Pressure

OK mate thanks might throw in a new one.

It’s been a while since I last changed one.
#243086 - in reply to #243071
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Posted 11/6/2021 12:36 PM
colsG55
Veteran


Date registered: Aug 2013
Location: Dubai
Vehicle(s): G55 Classic 2000, TD5 110, 200 Series Land Cruiser
Posts: 209
100
Re: Low Starting Fuel Pressure

The fault degenerated to the stage where there were several times I could not start the vehicle until waiting several hours for it to cool down, it also stalled a couple of times whilst sitting at traffic lights which was a real worry without knowing it would start again.

I have thrown in a new CPS and so far so good over the last week or so but time will tell if this is the final fix.
#243130 - in reply to #243071
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Posted 11/9/2021 5:59 AM
Inkblotz
Expert




Date registered: Apr 2006
Location: Georgia
Vehicle(s): 90 300GD "Thundering Turtle II", w/ 603A turbo
Posts: 3184
2000
Re: Low Starting Fuel Pressure

I have experienced Vapor lock on Benzes in the past, on a hot day with an old pump that was finally giving out. They would lock up till they cool down. Hopefully the new pump will continue to be the answer.
#243150 - in reply to #243071
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Posted 11/11/2021 12:16 AM
colsG55
Veteran


Date registered: Aug 2013
Location: Dubai
Vehicle(s): G55 Classic 2000, TD5 110, 200 Series Land Cruiser
Posts: 209
100
Re: Low Starting Fuel Pressure

So far so good, a couple of weeks since everything has been replaced and it seems to be running and starting perfectly again.

Lets hope it lasts.
#243152 - in reply to #243071
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