losing fuel pressure overnight ?

[Tractorat]

I just had a coolant drain and fill done last week at a dealer. I dont know if this is a coincidence or not. But I noticed that when I click the key 3 times I get a P0500 code.

I also noticed that when I start the truck after letting it sit overnight, it has to crank several times before it starts, like it doesnt have fuel pressure (?). Its never done that before.

Any ideas ?

Thanks

 

[Tractorat]

I guess the proper term is losing prime over night.

 

[BoeingDiesel]

Tractor, losing "Prime" would seem to point to a fuel leak but the P0500 is related to the speed sensor which you probably already knew. Have you noticed any drop in performance or fuel mileage...white smoke?

 

[DavidC]

This can lead to a slippery path. How much fuel in the tank ?. Suspects: VP overflow/bypass valve, leaky banjo bolt/washer, leaky injector, leaky high pressure O-ring and it goes on and on. If the tank is not full start there as it is the easiest.

Dave

 

[Tractorat]

Its about a quarter tank, but Ive never had the problem before, even with less fuel.
No white smoke. Im having an overheating issue that Im having looked at in about a week so I havent tried to stress anything. So, I dont know if there is any performance issue or not. I do show good fuel pressure although is seems like the needle flops around a little more that normat on startup. But that might be because I just hadnt paid that much attn to that before.

 

[DavidC]

I would fill the tank. There has been issues of the fuel pickup in the tank having cracks etc. causing back flow.

Dave

 

[Tinman]

Oddly, I have had this problem for years. Below half a tank of fuel, it will crank as if there is a little air in the line if left sitting overnight. The longer it sits, the worse it is. Front end up attitude makes it worse. If above half full, it will do it but it takes several days of sitting. At first, it was very bad, even sitting for a few hours it would do it. I noticed the rubber fuel lines (FASS pump) were cracking, so I replaced all of them, including the quick lock fittings at the fuel canister. This helped a lot, but it never went away. Also, during this time I have replaced Cross-over tubes (I've several sets of injectors and never did tubes. There was a little fuel in the oil on UOA once and replacing tubes fix this). And I put on a new VP -not related- and neither of theses made any difference at all. I finally gave up and just try to keep it more than half full. I'd love to fix it.

 

[gtwitch]

Ditto on the fuel level in the tank!! Seen this repeat itself many more times than o can count. Replace the draw straw in the tank and I don't know if you have the in tank pump but sounds like air is getting somewhere in the primary (low pressure side) of the system! I had a slight leak where I had put my pressure guage sending unit on the top of the filter housing , would not leak fuel out , but would leak air in after sitting over night and cooling, found that by spraying sopy water on all fittings and air bubbling out of that fitting but no fuel and as you would expect led to hard starts.
gtwitch in wyoming

 

[Tractorat]

Well, I actually had a problem with the connection at the tank last year. But I had a sump installed at the bottom of the tank. So that problem should be gone also. I do think I must be getting air in the system somehow though. Ill try spraying some soapy water around the fittings around the fass. If I dont see anthing there, Ill do the same in some other places as well. Thanks

 

[Tractorat]

I have a fass. I noticed that if I bump the starter a minute or so after shutting the engine down, the pump will run for about 30 seconds. Is the fass supposed to do that ? Or should the pressure from running keep it from having to do that ?

 

[DavidC]

Does the lift pump run on these no starts ?. I had an issue and noticed no fuel pressure then for no reason it would finally power up. There is a plug on the drivers side back by the fire wall that I cycled 2-3 times never actually unplugging all the way and have not had an issue since. I think the idea originated from a member Klamme (spelling could be wrong).

Dave

 

[DavidC]

I have a fass. I noticed that if I bump the starter a minute or so after shutting the engine down, the pump will run for about 30 seconds. Is the fass supposed to do that ? Or should the pressure from running keep it from having to do that ?

It will run whenever you bump the starter.

Dave

 

[Tractorat]

Does the lift pump run on these no starts ?. I had an issue and noticed no fuel pressure then for no reason it would finally power up. There is a plug on the drivers side back by the fire wall that I cycled 2-3 times never actually unplugging all the way and have not had an issue since. I think the idea originated from a member Klamme (spelling could be wrong).

Not sure. Ill see if I can find that plug and give it a try. Thanks

 

[Tractorat]

This issue only started after the dealer did the coolant service. Im trying to figure out what they might have done. I notice that there are a couple of hoses coming off the top of the original fuel filter box. If they had been fooling around and maybe bumped the water drain lever, could that cause this condition? I couldnt remember which way opened and which way closed it (and I guessed wrong). But I first opened it a little then pushed it all the way closed. I guess Ill find out if that made a diff in tomorrow morning.

 

[SnoKing]

What is your fuel pressure gauge telling you. When you bump the starter, does the pressure come right up? P0500 is a speed sensor code P0500 (M) No Vehicle Speed Sensor Signal No vehicle speed sensor signal detected during road load conditions. My 2001.5 set it all the time. DTT said it was from spinning the tires. SnoKing

 

[DavidC]

Not sure. Ill see if I can find that plug and give it a try. Thanks

Next time you try the start routine when this usually happens bump the starter first, listen for running pump and watch the pressure. On another forum a guy has a fass that has a return line and it has a plastic ball that had a groove that allowed drain back when not running. He contacted fass and changed the ball.

Dave

 

[Tractorat]

Next time you try the start routine when this usually happens bump the starter first, listen for running pump and watch the pressure. On another forum a guy has a fass that has a return line and it has a plastic ball that had a groove that allowed drain back when not running. He contacted fass and changed the ball.

Thanks. Ill give that a try tomorrow morning after its sat all night. Is your premise that it will not run at all ? Or that it will read low at first while the pump is running ?

 

[DavidC]

In my case it did not run at all then a little later it would turn on like it had to overcome the resistance in the electrical. That led me to that plug so I cycled the connection.

Dave

 

[Tractorat]

Thanks, It seems like I did that once and it did run. But maybe intermittant (?) Ill give it a try again in the morning.

 

[JR]

When you bump the starter after it's been sitting over night take notice as to how long it takes the fuel pressure to come up. If it comes up right away you may have another issue, if it takes a few seconds to several you've definitely got a small leak somewhere.
Generally a leak on the supply line side will be at least a little wet, perhaps not dripping wet but if your pump is putting out at least 12-15 psi any leak that is prevalent enough to siphon back while sitting should show while under pressure. The return line gets a little harder as it is not under pressure. As noted above check at the back of the head, this is a known trouble spot as these fuel systems age.
Also look your FASS over real well. I had an Air Dog on my 98 and when the seal went on the pump it created hard starts. The FASS is supposedly better quality but it is the same type construction that relies on a seal around the shaft of the motor to keep the fuel segregated to the pump side. When mine let loose fuel was actually leaking into the motor and dripping down the electrical connector.