lost fuel prime

[SF Jakey]

I've got a new baffling problem. In the last 2 weeks my fuel system has lost it's prime 3 times after sitting for as little as 3 days. Has anyone else experienced this and does anyone have a clue as to what might be causing it? I'm taking it to the dealer tonight, but I've found it best to get some info from the experts here before I go so I can at least have a dialogue with the service guy who is learning at about the same pace as me. Thank you AGAIN for all your replies.
P.S. Could this be connected to my poor fuel mileage?

[pullinpower]

The only thing I can think of would be your fuel filter allowing air in the system.I would check the tightness of it.Also check the black screw at the top to make sure its not worked loose.

[ 07-24-2002: Message edited by: pullinpower ]</p>

[Colorado Kid]

Maybe it's a Blue thing ;)

My buddy, who drives an Indigo Blue 2002 2500HD EC LB D/ZF 4x4 just recently went through the same symptoms. (Ended up 45 minutes late to work once). On his repair order the resolution was listed as "replaced fuel filter assembly due to leak". The problem has not reoccurred in the two weeks since the replacement. He did not mention any observed fuel economy problems, in fact some of you would say he was lying if I quoted his figures! (often better than 20).

Actually I do better than him ('cause mine's 2WD and I live farther out of town).

Since it seems to have been fixed on the first try, and since he got a free new fuel filter out of the deal, he's really not very upset about it. He did complain about having to drive a Cavelier the color of my truck though!

[ 07-24-2002: Message edited by: Colorado Kid ]</p>

[hickcox]

Make sure your fuel cap is on tight, The dealership replaced mine twice within the first few months after delivery, I had similar problem.
Also there is always a chance of a faulty check valve.

[SF Jakey]

THe dealership is claiming that my transferflow tank is the problem, which don't believe. Where is the check valve you're speaking of and how would a bad seal on a fuel cap cause an air leak to the system?

[Colorado Kid]

The tank is not likely to be the problem, and here is why I think so...

You say that your system is loosing prime when sitting, as in not running. It seems to me (not that I know anything) that a leak in the pickup tube of the tank would either let so little fuel out that it wouldn't cause a problem at all, or let so much air in that it would cause trouble all the time. I think you problem must be at or downstream from the fuel filter, becasue I think that the filter itself must be at least partially filling with air to cause the problem.

The fuel cap is vented, so I really don't think it can cause the trouble. I can't imagine why hickox had to have two replaced.

I don't know anything about check valves in our fuel systems. There may be (probably is) one somewhere, but I wouldn't know where.

[YZF1R]

I believe the fuel cap may be vented for presure but is not for vacuum. At least to a point. If the cap is not on tight it will throw a code. It can happen if the cap is off while fueling and the engine is left running.

Steve

On edit: I guess the cap would have to be off while fueling. :rolleyes:

[ 07-25-2002: Message edited by: YZF1R ]</p>

[mackin]

Actually I think driving with a loose cap or no cap will toss an SES...... I seldom shut mine off while fueling, never seen a code, then again my truck is "BLACK".......


MAC smile.gif

[mdrag]

SF Jakey,

You did not mention your total mileage and mileage since the TFI install. I would check the fuel line connections between the tank and fuel cooler to see if there were any signs of leakage etc. I also suggest changing the fuel flter. After my TFI install, I changed the fuel filter after 2K-3K miles. TFI recommends changing the fuel filter within a few K miles of the tank install - but I don't recall the exact recommendation...

There are pics of a cut open OEM fuel filter at the first link in my sig, choose the Oil/Fuel Filter comparison album or cut and paste this link:

http://www.picturetrail.com/gallery/view?p=999&gid=526359&uid=157168

My OEM filter was quite discolored at 4.6K total miles :eek:

The filler cap on/off will not set a SES on the '01 DMAX, and I have not read anything that this changed for '02. Taking the cap off on a gasser while running is a different matter and will set an SES. As a test, I parked my '01 3500 D/A in my shop with the fuel cap off for almost 1 week (after the TFI install) started it up and drove around for a few miles. No problems starting and no SES light or DTCs resulted.

Good luck.

[YZF1R]

OK. Thought I read on here about a year ago of someone throwing an SES while fueling with engine running. Thanks for the correction!

Steve

[SF Jakey]

Well, the dealer changed the fuel filter and the problem has supposedly stopped. This doesn't add up to me, but then again I'm new to diesels. Who knows, maybe this will help me see some mileage numbers over 15.5 as well. Dealer claims that my 285's are the reason for the poor mileage, but I find it hard to believe a truck with this much power is affected that easily. Besides, bigger tires means lower rear end ratio wich equals lower rpm's and better economy, right. Anyway, thank you for your replies and help. Hopefully I can share some knowledge that will help someone here also.

[ndamico]

It is my understanding that all OBD-II vehicles will throw a code without a fuel cap. However out lovely Dmax's aren't OBD-II, at least as far as the fuel tank goes. I asked transfer flow when i went to have my replacement tank installed and that's what they told me. maybe i should go start up my WHITE truck mackin' and see if it stands the test like yours! :D :D

[SoCalDMAX]

I also remember a post like YZF1R described. Someone had a mysterious SES code and another member pointed out that leaving the engine running while fueling could do it.

Maybe it was mass hypnosis and we're both imagining it... tongue.gif

Regards, Steve

[ 07-26-2002: Message edited by: SoCalDMAX ]</p>

[Tommy turbo]

Our system is obdII (On Board Diagnostics) It will not set a code while sitting stil refueling with the cap off. The computer pressurizes the evap system (fuel Tank) after the speed of the vehicle is over about ten miles per hour and a couple of other things have been met. If it leaks off pressure in a given time frame it will set a code. (I have never run an evap test on my diesel however so it may not even have this system in place)

[ 07-26-2002: Message edited by: Tommy turbo ]</p>

[YZF1R]

SoCalDMAX: Thanks, I thought I remembered something like that too.

Steve

[Spoolin'It]

SF Jakey,

I bet the filter was the source of your problems. I had a similiar problem over the winter, the drain valve assembly at the bottom of the filter came unscrewed and the truck was sucking air while running but wasn't leaking anything noticeable when shut off.
It finally stalled one night, after it had been running all day and wouldn't restart. I found the air leak when I reprimed it and fuel started pouring out of the bottom of the filter.

[SF Jakey]

Sorry to beat this horse more, but the truck lost its prime after having the filter changed and having the fuel system pressure tested for leaks. Fuel economy has really gone down again, 11 mpg @65 mph to Tahoe and back. I love this truck, but these problems are starting to remind me of my old f***. Any ideas would really help, because GM knows nothing. By the way, there is no sign of fuel going anywhere, no odor, and no rise in oil level.