Fuel Delivery Problem
04-19-2019, 12:53 PM
#1
Fuel Delivery Problem
The low fuel indicator lit up, the gauge showed a little above empty, and about ten to fifteen miles later the ‘89GT showed every symptom of running out of gas: loss of power, rough running, unhappy idle, etc. A convenient gas station allowed me to avoid indignity and the car ran fine after filling the tank.
The problem is that topping the tank only took 18.9 gallons. This is not close to the twenty three that should be required to fill an empty tank. Either the tank has shrunk or I have another problem….
I haven’t started to trouble shoot this yet and wanted to ask what the likely source might be. I suspect that I am not the only one to have had this problem.
The tank has a screened outlet (the internal pump was removed some years ago, the filter has a few thousand miles on it, all the hoses are new (~three years - mostly Greg Brown’s), and I have no idea about the fuel pump.
My plan, such as it is, is to check fuel pressure and delivery (BTW, the WSM does not seem to describe - or I failed to find the reference - how to check the fuel delivery quantity of 1250 ml in 30 seconds). I will replace the external filter and remove and inspect the screened outlet from the tank when there is not so much fuel to drain, and might even refurbish the old internal pump and put it back in.
Comments and helpful suggestions are always appreciated. Thanks!
The problem is that topping the tank only took 18.9 gallons. This is not close to the twenty three that should be required to fill an empty tank. Either the tank has shrunk or I have another problem….
I haven’t started to trouble shoot this yet and wanted to ask what the likely source might be. I suspect that I am not the only one to have had this problem.
The tank has a screened outlet (the internal pump was removed some years ago, the filter has a few thousand miles on it, all the hoses are new (~three years - mostly Greg Brown’s), and I have no idea about the fuel pump.
My plan, such as it is, is to check fuel pressure and delivery (BTW, the WSM does not seem to describe - or I failed to find the reference - how to check the fuel delivery quantity of 1250 ml in 30 seconds). I will replace the external filter and remove and inspect the screened outlet from the tank when there is not so much fuel to drain, and might even refurbish the old internal pump and put it back in.
Comments and helpful suggestions are always appreciated. Thanks!
04-19-2019, 01:12 PM
#2
Rennlist Member
The low fuel indicator lit up, the gauge showed a little above empty, and about ten to fifteen miles later the ‘89GT showed every symptom of running out of gas: loss of power, rough running, unhappy idle, etc. A convenient gas station allowed me to avoid indignity and the car ran fine after filling the tank.
The problem is that topping the tank only took 18.9 gallons. This is not close to the twenty three that should be required to fill an empty tank. Either the tank has shrunk or I have another problem….
I haven’t started to trouble shoot this yet and wanted to ask what the likely source might be. I suspect that I am not the only one to have had this problem.
The tank has a screened outlet (the internal pump was removed some years ago, the filter has a few thousand miles on it, all the hoses are new (~three years - mostly Greg Brown’s), and I have no idea about the fuel pump.
My plan, such as it is, is to check fuel pressure and delivery (BTW, the WSM does not seem to describe - or I failed to find the reference - how to check the fuel delivery quantity of 1250 ml in 30 seconds). I will replace the external filter and remove and inspect the screened outlet from the tank when there is not so much fuel to drain, and might even refurbish the old internal pump and put it back in.
Comments and helpful suggestions are always appreciated. Thanks!
The problem is that topping the tank only took 18.9 gallons. This is not close to the twenty three that should be required to fill an empty tank. Either the tank has shrunk or I have another problem….
I haven’t started to trouble shoot this yet and wanted to ask what the likely source might be. I suspect that I am not the only one to have had this problem.
The tank has a screened outlet (the internal pump was removed some years ago, the filter has a few thousand miles on it, all the hoses are new (~three years - mostly Greg Brown’s), and I have no idea about the fuel pump.
My plan, such as it is, is to check fuel pressure and delivery (BTW, the WSM does not seem to describe - or I failed to find the reference - how to check the fuel delivery quantity of 1250 ml in 30 seconds). I will replace the external filter and remove and inspect the screened outlet from the tank when there is not so much fuel to drain, and might even refurbish the old internal pump and put it back in.
Comments and helpful suggestions are always appreciated. Thanks!
Disconnect the return hose at the fuel level sender, run a hose from it outside the hatch into a jug, jumper the FP relay and count to 30.
04-19-2019, 01:20 PM
#3
Drifting
Is it true the 928 has a 23 gallon fuel tank?
At 17 mpg that's 391 mile range.
When I'm down to 1/4 tank, my odometer shows 250 miles which means I still have roughly 9 gallons of gas in the tank which seems like a lot of gas for an indicated 1/4 of a tank remaining.
At 17 mpg that's 391 mile range.
When I'm down to 1/4 tank, my odometer shows 250 miles which means I still have roughly 9 gallons of gas in the tank which seems like a lot of gas for an indicated 1/4 of a tank remaining.
04-19-2019, 01:33 PM
#4
Rennlist
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The tank is made with a main section and a higher filler neck section. There is a hose that connects these two sections, so that air doesn't get trapped in the main secrion, when the filler neck section fills enough to "seal off" the main section.
If this hose gets crimped shut, the tank will not fill completely. Although this is not common if the tank has never been removed, it is very common if it has been removed....almost everyone installs the hose bavkwards, which will crimp it shut.
The other common failure is for the charcoal canister "purging system" to fail, which exposes the tank to excessive vacuum and sucks it in. This is easy to see, from the bottom of the tank.
If this occurs, the tank almost always will require replacement (it will eventually crack and leak at the "fold" caused from the sucking inward.)
I keep multiples of both used and new tanks, in inventory (for sale), because of this issue.
If this hose gets crimped shut, the tank will not fill completely. Although this is not common if the tank has never been removed, it is very common if it has been removed....almost everyone installs the hose bavkwards, which will crimp it shut.
The other common failure is for the charcoal canister "purging system" to fail, which exposes the tank to excessive vacuum and sucks it in. This is easy to see, from the bottom of the tank.
If this occurs, the tank almost always will require replacement (it will eventually crack and leak at the "fold" caused from the sucking inward.)
I keep multiples of both used and new tanks, in inventory (for sale), because of this issue.
04-19-2019, 01:41 PM
#5
Rennlist Member
Do you live in a hot climate Stateside?
In my experience when the fuel is low at the levels you replenished and with an in tank pump fitted a hard draw on the engine will produce hesitation on hot days. Without the in tank pump it can only get worse. Idle is usually OK though.
In my experience when the fuel is low at the levels you replenished and with an in tank pump fitted a hard draw on the engine will produce hesitation on hot days. Without the in tank pump it can only get worse. Idle is usually OK though.
04-19-2019, 02:31 PM
#6
When working properly, the light should come on and you will get to shove about 18 gallons in, leaving 4 in the tank as a reserve. The most I've taken mine down to was 2 gallons left, or filling 20 in. Our tanks are 22 gallon.
04-19-2019, 03:50 PM
#7
Drifting
Trending Topics
04-19-2019, 04:06 PM
#8
Chronic Tool Dropper
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Lifetime Rennlist
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Check your in-tank pump. 
04-20-2019, 01:04 AM
#9
Thanks for the quick responses.
Capacity – the specs say the tank holds 23 gallons. I have previously filled more than twenty gallons on several occasions and gotten far more than ten or fifteen miles after the low fuel indicator lit up; and with no threat of fuel starvation.
Tank vacuum/ tank balance hose – no sucking sound reminiscent of the various taxing authorities when I removed the gas cap. I had removed the tank long ago and replaced the hose exactly as it was (somewhat of a PIA as I recall)…. hopefully it was correct to begin with… but I will check it for kinks and the tank for “shapeliness”.
Air temperature was in the low 60’s F. FWIW, temperatures last summer exceeded 100 F many times with no fuel issues (and no internal pump).
I will do the visual inspections and test the fuel pump pressure and volume with the nearly full tank in the next day or so. If the results are not alarming, I will wait until I have less than a quarter tank before performing any surgery (I can’t conveniently store more than a few gallons of gas).
I try to be thorough (although I sometimes fail more than I care to admit…), so I will start with the tank itself and the internal screen (and might put the in-tank pump back in), and proceed from there.
Capacity – the specs say the tank holds 23 gallons. I have previously filled more than twenty gallons on several occasions and gotten far more than ten or fifteen miles after the low fuel indicator lit up; and with no threat of fuel starvation.
Tank vacuum/ tank balance hose – no sucking sound reminiscent of the various taxing authorities when I removed the gas cap. I had removed the tank long ago and replaced the hose exactly as it was (somewhat of a PIA as I recall)…. hopefully it was correct to begin with… but I will check it for kinks and the tank for “shapeliness”.
Air temperature was in the low 60’s F. FWIW, temperatures last summer exceeded 100 F many times with no fuel issues (and no internal pump).
I will do the visual inspections and test the fuel pump pressure and volume with the nearly full tank in the next day or so. If the results are not alarming, I will wait until I have less than a quarter tank before performing any surgery (I can’t conveniently store more than a few gallons of gas).
I try to be thorough (although I sometimes fail more than I care to admit…), so I will start with the tank itself and the internal screen (and might put the in-tank pump back in), and proceed from there.
04-22-2019, 11:51 AM
#10
Rennlist Member
My low fuel light typically comes on with around 18 gallons to fill as well, and I can confirm that it will take 23 gallons from empty. When I first got my 85 the fuel sender was stuck and I ran it empty on the drive home. I'd be inclined to pull the in-tank strainer (once you're back closer to empty) and see if it is getting occluded and causing a pressure drop to the pump when you have low head pressure in the tank.