resent trip ends in head scratching

kokenm · kokenm's Garage

I resently was able to get my 911 sc running and worked out many of the kinks.
I took a ride with my son for 2hours. The car ran beautifully until all of a sudden it started to act as though there was water in the gas ( bucking and missing). I pulled off to the side of the road and kept the car at idle until what I thought was water cleared out and then took off. I ended up doing this two more times on the way home.
Next morning i got in the car to drive to work and the same thing happened.
I put Gas additive in the tank to remove the water but that does not seem to be the issue. As I was stranded with an engine that coughed and sputtered for about 45 minutes I noticed that the gas guage was taking a dramatic hit. I had the car towed back to the house and when I put it in the garage I spent a lot of time airing out the garage from the fuel smell.

I appeal to the knowledge of the forum for help. I am at wits end with this one.

Mike

ossiblue · 12-09-2013, 06:35 AM

I take it from your post that the gas gauge taking a hit means the level of gas dropped dramatically, correct? That, plus the gas smell in the garage makes it sound like you have a serious leak in one of the high pressure gas lines which could cause loss of fuel pressure/volume or even allow air bubbles to enter the FD, leading to bucking and hesitation. Regardless, there should be no gas smell coming from the vehicle.

If the meaning of gas gauge taking a hit is that the needle was wildly bouncing or moving erratically, then you may have an electrical problem that is causing ignition problems (bucking) and resulting in unburned fuel remaining in the engine.

kokenm · kokenm's Garage

Yes the amount of Gas in the tank dropped dramatically. The Gas guage did not move erratically it was steadily dropping. I will look for a leak in the high pressure gas lines.

Lapkritis · Lapkritis's Garage

Check your oil - likely full of fuel if you have a misfire and the fuel went unburnt. Nice way to clean the inside of your engine but not so good for bearings so good to check out.

Could be weak spark cause by old plugs, worn ignition items (cap, rotor, points?), moisture causing shorts etc...

dnovick911 · dnovick911's Garage

And now for my entry into the "master of the obvious awards"...I would NOT drive that car until leak found and remedied.

kokenm · kokenm's Garage

The vehicle is not moving until this issue is resolved.

david.avrahami@ · david.avrahami@'s Garage

It is probably your fuel pump relay underneath your car seat ...see if you can shake it...

kokenm · kokenm's Garage

Andrew,
New plugs, cap and rotor. I cannot imagine that those would cause such a great loss in fuel.

I will drain the oil and look for fuel. Seems like I should start investing in mobil one stock with as many times as I have drained oil for engine removal and such.

Don't want to leave any stone unturned.

Mike

kokenm · kokenm's Garage

David will look at fuel pump relay. I guess I need to make a list.

Thanks guys
Mike

Jdub · 12-09-2013, 07:20 AM

Just adding to be sure to swap out the fuel filter. It packs itself full of the crap we put into our cars via the fuel tank. Thanks to Ethanol, it can build up a nice waxy substance that can cause issues. I replace mine twice a year - not too often with our CIS systems!

Do put this on your list of To-Dos. Best of luck and keep us posted!

kokenm · kokenm's Garage

I believe that I have a new Fuel Filter. I will do that also.
thanks Jdub

kokenm · kokenm's Garage

interesting note: It was running better than I had ever had it running. I had the wind in my sails and life was beautiful for a couple hours.

jpnovak · 12-09-2013, 07:36 AM

The fuel additive may have released some of the build-up and crud in the tank. Pull your gas sender and shine a flashlight down in there. Look for fine brown sediment in the bottom of the tank.

I suspect you need to pull the tank and clean it. You can start with the filter screen in the outlet of the tank. If this is clogged it will not flow fuel except at idle.

Be aware the fine sediment can kill a fuel pump and clog fuel filters.

I would not change oil until I verified these two things. You can also check your control pressure at the WUR to see if you are in spec.

Do the injectors sing when the metering plate is lifted? Have you pulled each injector, placed it in a bottle and checked fuel spray patterns? This will help you look for fuel pressure or volume delivery problems.

Steve@Rennsport · 12-09-2013, 08:05 AM

Quote:

Originally Posted by jpnovak

I suspect you need to pull the tank and clean it. You can start with the filter screen in the outlet of the tank. If this is clogged it will not flow fuel except at idle.

Excellent advice from Mr. Novak (all of it), I'd just add that your in-tank filter is located at the bottom of the tank, not at the outlet and return. Look for a big hex plug at the bottom and thats the base of the filter assembly. Its a replacement item.

kokenm · kokenm's Garage

I can understand all of this although I am still not sure I understand why there was such a great fuel consumption if the fuel system was clogged.

jasonlee · 12-09-2013, 10:48 AM

I had a similar issue with my SC, turns out it was the relay under the seat and a clogged fuel filter. That said, it does not explain the dramatic loss in fuel, but certainly would address those items.

kokenm · kokenm's Garage

Alright then. a fuel system diagnostics and filter replacement. will make sure to check issues with pressure and leaks. relay is first on the list.

Thanks all for the input.
At least I have a start. Seems like just when I get things going I run into another issue. very frustrating but I love the ride.

Mike

ossiblue · 12-09-2013, 01:25 PM

Something else to add to the mix. If the excessive fuel consumption is not from an external leak (my first inclination from your OP), then an internal leak from a bad injector or leaking cold start valve may be a consideration. Your statement about how well it ran before the symptoms appeared strike me as a possible overly rich situation. If the gasoline smell you mentioned was coming from inside the crankcase/oil tank rather than from an external leak, then raw fuel was being dumped inside by some mechanism.

racicotzhe · 12-09-2013, 06:05 PM

The Gas guage did not move erratically it was steadily dropping.

Cattler · Cattler's Garage

+1 and +1 on these. I had the same symptoms as the OP and found the problems these guys have suggested. My fuel tank had a fine grey foam on top of the fuel, the fuel filter was clogged with light grey stuff that felt like graphite, and I also replaced the fuel pump (noisy). Note that its worth replacing the short runs of fuel hose going to / from the fuel pump while you're there doing the work. You'll likely find that these have the beginnings of some cracks.

Quote:

Originally Posted by jpnovak

The fuel additive may have released some of the build-up and crud in the tank. Pull your gas sender and shine a flashlight down in there. Look for fine brown sediment in the bottom of the tank.

I suspect you need to pull the tank and clean it. You can start with the filter screen in the outlet of the tank. If this is clogged it will not flow fuel except at idle.

Be aware the fine sediment can kill a fuel pump and clog fuel filters.

I would not change oil until I verified these two things. You can also check your control pressure at the WUR to see if you are in spec.

Do the injectors sing when the metering plate is lifted? Have you pulled each injector, placed it in a bottle and checked fuel spray patterns? This will help you look for fuel pressure or volume delivery problems.

Quote:

Originally Posted by Steve@Rennsport

Excellent advice from Mr. Novak (all of it), I'd just add that your in-tank filter is located at the bottom of the tank, not at the outlet and return. Look for a big hex plug at the bottom and thats the base of the filter assembly. Its a replacement item.