Fuel Pressure problem?
Thread Starter
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Freshman User
Joined: Sep 2009
Posts: 27
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Well I borrowed a fuel pressure guage and this is what i've found
key on primes @42 psi
stops priming 39psi
cycle key it does not build any addational pressure.
Starts after 10 key cycles runs @34 psi.
As far as I can tell these are all within specs.
I'm stumped, any other ideas??
key on primes @42 psi
stops priming 39psi
cycle key it does not build any addational pressure.
Starts after 10 key cycles runs @34 psi.
As far as I can tell these are all within specs.
I'm stumped, any other ideas??
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 13
From: Sand Lake, MI
Well I borrowed a fuel pressure guage and this is what i've found
key on primes @42 psi
stops priming 39psi
cycle key it does not build any addational pressure.
Starts after 10 key cycles @34 psi.
As far as I can tell these are all within specs.
I'm stumped, any other ideas??
key on primes @42 psi
stops priming 39psi
cycle key it does not build any addational pressure.
Starts after 10 key cycles @34 psi.
As far as I can tell these are all within specs.
I'm stumped, any other ideas??
How much pressure does it build from zero when turning the key to "run" just one time (35 to 45psi), then how much pressure does it hold running at an idle (30 to 45psi), and then with the vac line removed from the fpr (just put your thumb on the vac line to plug it while reading the gauge) (should increase 5 to 10psi).
You may find the pressure is within spec more often then not, you need to check it when it will not start.
Thread Starter
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Freshman User
Joined: Sep 2009
Posts: 27
Likes: 0
Yes it won't start with 39 psi unless you cycle the key 10 times.
Turn on the key it primes at 42 psi and then39 psi when the pump stops.
Remove the vacuum line from the fpr and pressure increses 10 psi when running.
I just did a compression test and all the cylinders are between 100 &118 psi except 1-45 psi and 2 -95 psi looks like it maybe more serious than I'd hoped
Turn on the key it primes at 42 psi and then39 psi when the pump stops.
Remove the vacuum line from the fpr and pressure increses 10 psi when running.
I just did a compression test and all the cylinders are between 100 &118 psi except 1-45 psi and 2 -95 psi looks like it maybe more serious than I'd hoped
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 13
From: Sand Lake, MI
Yes it won't start with 39 psi unless you cycle the key 10 times.
Turn on the key it primes at 42 psi and then39 psi when the pump stops.
Remove the vacuum line from the fpr and pressure increses 10 psi when running.
I just did a compression test and all the cylinders are between 100 &118 psi except 1-45 psi and 2 -95 psi looks like it maybe more serious than I'd hoped
Turn on the key it primes at 42 psi and then39 psi when the pump stops.
Remove the vacuum line from the fpr and pressure increses 10 psi when running.
I just did a compression test and all the cylinders are between 100 &118 psi except 1-45 psi and 2 -95 psi looks like it maybe more serious than I'd hoped
The pump should run for two seconds and quit, the computer has no idea how much pressure there is, just primes for two seconds and stops.
You have a counter productive cylinder, the one with the compression reading of 45psi, the others while low are not a issue other then they show wear.
The really low cylinder is a problem, it is likely causing lots of blow by back into the intake, it will cause havoc with the SD system if it is. If its a exhaust valve leak not so bad, a loss yea but at least it won't interfere with the induction system if it is.
To get a idea what kind damage it has pour couple three tablespoons full of clean motor oil down the plug hole into that cylinder that read 45 psi and compression test it again, see if the compression value rises. If it does it is ring wear, if not it is a mechanical failure of some kind and needs looked at. Might just be a head gasket or a valve train issue easily repaired. Doubt it but worth checking out.
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To get a idea what kind damage it has pour couple three tablespoons full of clean motor oil down the plug hole into that cylinder that read 45 psi and compression test it again, see if the compression value rises. If it does it is ring wear, if not it is a mechanical failure of some kind and needs looked at. Might just be a head gasket or a valve train issue easily repaired. Doubt it but worth checking out.
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 13
From: Sand Lake, MI
What does that do? Just trying to learn something new here... Thanks.
The oil is thick and takes up some space so if the rings/cylinder is worn allowing blow by the oil will aid in sealing them raising the compression value.
At the same time the oil even though thick it can only take up so much space so with a hole burnt in a piston, broken rings or a valve leak or any type of severe mechanical failure the oil can't improve the seal and increase the compression value.
The oil is thick and takes up some space so if the rings/cylinder is worn allowing blow by the oil will aid in sealing them raising the compression value.
At the same time the oil even though thick it can only take up so much space so with a hole burnt in a piston, broken rings or a valve leak or any type of severe mechanical failure the oil can't improve the seal and increase the compression value.
