Home » Public Forums » GMCnet » [GMCnet] Jim Bounds interesting recent posts
| [GMCnet] Jim Bounds interesting recent posts [message #325926] |
Fri, 10 November 2017 15:31  |
glwgmc
Messages: 1014
Registered: June 2004
Karma: 10
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Senior Member |
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Hi Rick,
No can should be left open here no matter what the contents! (grin). Our 40 plus year old motorhomes and their owners need all the help they can get no matter where it comes from.
I never heard back from the new owner of that coach as to what the root cause was so I have no idea if it was throttle body electronic related, fuel command center related, a loose wire somewhere, a failed fuse or relay, a module or coil failure in the HEI, or what. At the time he referred to the FiTech throttle body as an “electronic carburetor” and he reverted back to the carburetor stored in the pod to get home to AK. I don’t know if the FiTech throttle body ever went back on or not. He also had an issue with the Pertronics module in the generator (a loose ground wire according to the fellow who did the repair) but that was found after they reverted back to the points so I don’t know if the Pertronics module ever got back into service either.
The speculation about heat being the root cause issue with the coach not starting after a fuel stop was just that, speculation. There are a bazillion FiTech (and other) self learning EFI systems in service in all kinds of vehicles. Many of those now feature electronic controls inside the throttle body so I just don’t think that is an inherent issue.
I rarely hear about any FiTech failures in GMCs, but the few times I have heard of such it seems more related to something amiss in the fuel command center than it is with the throttle body. One person found a loose clamp on a hose inside the Fuel Command Center. Once that was tightened I have not heard of any other issues there. Another person found an apparently failed high pressure fuel pump inside the Fuel Command Center and once it was replaced I think that one worked just fine afterward as well. Side bar, I note that Jim Bounds does not use the Fuel Command Center, instead he has his people mount a high pressure fuel pump on the outside of the frame rail and he tosses another into the spares compartment on board.
On initial set up some people were confused by what it meant to set the mechanical stops on the throttle to produce what the instructions called "6 to 10 steps”. That referred to the number of steps the stepper motor controlling the air bypass needed to move in order to set the throttle position sensor to the correct position. The throttle position is a critical factor in calculating the proper injection duration so if that is not set right, the whole fuel curve would be effected.
Other than things like that I have not heard much about FiTech units not working correctly for our motorhomes in the field. I know there are a lot of them out there so they must be ok for most owners.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
glwork@mac.com
http://jerrywork.com
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Message: 3
Date: Fri, 10 Nov 2017 18:03:51 +0000
From: Richard Denney
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] Jim Bounds interesting recent posts
Message-ID:
Content-Type: text/plain; charset="UTF-8"
Jerry, I don't want to open a can of worms, but the longevity of the FITech
unit, with its electronics in a sometimes very hot throttle body, has been
questioned. One of the coaches you sold had a FITech system and suffered a
sudden fuel delivery failure for the new owners on their trip home. What
was the final diagnosis of that failure? There was speculation at the time
about effect of heat on the electronics……….
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Jerry & Sharon Work
78 Royale
Kerby, OR
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| Re: [GMCnet] Jim Bounds interesting recent posts [message #325927 is a reply to message #325926] |
Fri, 10 November 2017 17:05  |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
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Senior Member |
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FYI. I have been running a FiTech now for about 3K miles, and have had two issues, both of which were not really FiTech related. I post this only because if others run into the same symptoms, they will have a starting point on where to look.
Let me start with what I have. I am running a Cadillac 500 and have had it powered by a Qjet that was stock for the Cad engine, a Qjet that was altitude compensating, a Port EFI with EBL software, and now the FiTech. Best performance hands down is from the FiTech. My fuel system consists of 25gal fuel tanks. High pressure fuel pumps are in the tanks and controlled by a switch on the dashboard. Once activated by dash switch, fuel flows through a check valve located at each tank. Check valve keeps fuel from flowing into the nonactivated pump and into the other tank. Fuel continues to a "T" in the line allowing pressure to build at the Fuel Pressure Regulator. Once calibrated pressure is reached, excess fuel is dumped back into the front fuel tank, the "reserve" tank. Pressurized fuel then flows through another check valve which keeps fuel under pressure for "hot restart". Fuel then flows through an inline fuel filter and on to the "dead head" FiTech throttle body.
The system is designed this way with the pressure regulator located on the frame rail at the front tank to keep fuel from going to the engine, heated up by engine heat, and returned to the tank hot, thereby increasing the chances of vapor-lock.
Now that you know what I have, here are the two issues I delt with when I installed the FiTech. First issue...shortly after the install, the motor just suddenly started running VERY rich, like I mean AF ratios were in the low 11's, high 10's. Now that was averaging 10.8/1 FA. After looking at several things, decided to get a Fuel Pressure gauge and check to see that FP was at the spec'd 58lbs. So I let the engine run while I went looking for the gauge. When I got back I noticed that the FiTech TB was soaking wet with water, and ice cold to the touch. Also found the vacuum line going to the PCV valve was also cold and wet, as was the "T" in the line and hose that went to the vacuum canister. Disconnected the vacuum line going to the canister and plugged it. Instantly the engine smoothed out and AF went into the 14's. What I found was the Vapor separator (located in the left rear wheel well) had malfunctioned and was allowing a full fuel tank to bleed raw fuel through the canister and into the TB below the throttle plates. The change in physical state from liquid to vapor caused the cold TB and condensation on the TB. And most of all caused the excessively rich mixture as indicated by the AF readout. I now have replaced the Vapor separator and all is well. This issue, not the fault of the FiTech. Who KNEW!!
The second issue cropped up when I would stop for fuel after several hours traveling and a hot engine. The engine would not restart after refueling...not all of the time, just intermittently. When you turn the key on with the FItech, yours should hear a clicking sound coming from the TB. That is the software opening the throttle plates slightly and squirting some fuel into the intake manifold for a clean start. When I had the no start condition, I was not hearing the clicking and not seeing the throttles click briefly open. Apparently there is a sensor of some kind in the TB that sensed fuel presence. No fuel...no squirt. Somehow a bubble of air or maybe fuel vapor gets caught as a bubble in the TB and since it senses no fuel...no start. To start, I take a adjustable wrench, and crack open one of the fuel inlets to let the bubble out. Instant start and no issues until the no start happens again. I think this is a kind of vapor lock happening in the TB after a hot run. This may well be a result of not having a return line to the tank. When FP exceeds the 58lbs, there is no way to bleed off this pressure. So, I'm working on a solution to this..not sure what it will be.
Again, I post this so that it might help anyone experiencing these same symptoms and for people to take preventive measures. Hope this helps someone.
Larry 
78 Royale w/500 Caddy
Menomonie, WI.
[Updated on: Wed, 15 November 2017 16:49] Report message to a moderator |
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