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Car Forum / Ford / Ford Trucks / July 20066.5L diesel surge on low fuel
Had an odd thing happen today. Crusing along at 70mph and fuel tank is close to empty but not quite, and suddenly I get a surge of power that felt like a turbo kicking in (not a turbo vehicle), and it went up to 80mph without moving the pedal. Then as suddenly as it happened it dropped back to 70. It did this about 5 times over a 10 minute period. I swapped tanks and filled up a few miles down the road and the tank proved not to be empty. Could this be bubbles coming through the fuel line and changing the air/fuel mix ? I would think this would drop power off not boost it. I will be interested to hear some ideas. (whitelightning ? spdloader ? ) woodee Did you have your cruise control engaged? I'd guess something is faulty with the cruise or your VSS, I don't think it was a fuel issue, just a coincidence that it happened with an almost empty tank. If you mean 6.0L diesel (what year, model?) it has throttle by wire so the pedal doesn't move when the cruise is engaged, it just flops down to idle position. Took me a while to get used to that. Now that I mention it, it might be a problem with your pedal position sensor, or the throttle motor, or the EEC.... > Had an odd thing happen today. Crusing along at 70mph and fuel tank is > close to empty but not quite, and suddenly I get a surge of power that [quoted text clipped - 8 lines] > > woodee I guess I should have given a more accurate description of the truck. Its a 1986 F350 4x4 with a 6.5L chevrolet diesel conversion. see - www.brunswickdiesels.com.au No cruise control, manual transmission, mechanical injector pump. Either I have had a faulty pump from new, and its suddenly getting the right amount of fuel - or perhaps its a faulty pump now and injecting too much fuel. Darren > Did you have your cruise control engaged? I'd guess something is faulty with > the cruise or your VSS, I don't think it was a fuel issue, just a [quoted text clipped - 18 lines] >> >>woodee >I guess I should have given a more accurate description of the truck. > Its a 1986 F350 4x4 with a 6.5L chevrolet diesel conversion. > see - www.brunswickdiesels.com.au Sacrilige. :-) Did you try a Chevy group? Or perhaps you should contact Brunswick...that kind of conversion isn't very common in the USA. > No cruise control, manual transmission, mechanical injector pump. > Either I have had a faulty pump from new, and its suddenly getting the [quoted text clipped - 25 lines] >>> >>>woodee > I guess I should have given a more accurate description of the truck. > Its a 1986 F350 4x4 with a 6.5L chevrolet diesel conversion. [quoted text clipped - 6 lines] > > Darren If you start sucking air the power drops like a rock, and sometimes the engine will really start to clatter. Remember we are talking compression ignition, if the fuel mix goes too lean, combustion temps go through the ceiling and you can get re-ignition, which can really do a number on a diesel, worse than on a gasser. what hasn't been said is, Did changing tanks cause the issue to go away? Has it done it since? How much black smoke are you making? And since you say mechanical injection system, I would say get it checked out by a mechanic. Back in the days when I wore OD Green for a living, the most antsy time was starting a diesel for the very first time, especially the M123's with the V-8 Mack engines, and the M113 APC with the detroits. If the pumps weren't set up right the engine would "run away". We kept a thick hard cover repair manual on the fender, with the air filter not connected so we could throw it over the intake opening to shut a run away down. It didn't always work. in which case people were diving for cover. Whitelightning > Had an odd thing happen today. Crusing along at 70mph and fuel tank is > close to empty but not quite, and suddenly I get a surge of power that [quoted text clipped - 8 lines] > > woodee My experience with that is with the bigger diesels, Caterpillar, etc. Usually, something in the high pressure pump goes awry, only for a moment, and suddenly you have a tremendous surge of power. It is a warning of things to come. If the pump regulator goes bad and you get full fuel to the cylinders, you'll get exactly what whitelightning was talking about, a runaway. How'd you like to be hauling a load, say 80,000lbs, headed toward a stoplight, 10 cars or so in front of you, and suddenly it happens, and the damn thing won't stop. Happened to me. Aged me about 10 years. I had to have the high pressure pump rebuilt, and it has run like a top since. Let me say again though, that my only experience with your specific problem, has been with the big diesels. I haven't seen it in a smaller one. Keep the group posted, if you will. Spdloader I may have discovered part of the problem. Being an old truck it has dual fuel tanks and an automatic switching valve that works off the tank pump pressure selecting where to get fuel from and where to return it to. I found very little was getting past this, and the pipe from this to the filter on the firewall was partially blocked / crimped under the cab. I also think the pressure coming from the tank pumps is insufficient, I am trying to find out now if they have filters on the pickup. I read someone else's post somewhere where they were getting foam instead of straight fuel and getting surges of power. woodee > Had an odd thing happen today. Crusing along at 70mph and fuel tank is > close to empty but not quite, and suddenly I get a surge of power that [quoted text clipped - 8 lines] > > woodee |
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