February 10, 2017

In my last post I said I didn’t like the way my vacuum switch was working. I bought the adjustable switch from Dave Lenzi and he said to adjust it so that my pump turned on at 16 inches of mercury and off at 18 inches. I did that but because my engine only pulls 15 inches, the pump turns on every time I use the brakes. I asked Dave about this and he said that the booster works best at 16 inches or more and that a normal engine should be able to pull about 18 inches at sea level.  He said that for each 1,000 feet of altitude above sea level that number will go down by 1 inch. I am at about 2,600 feet at home. That would make my vacuum at sea level be almost 18 inches and my pump would not be coming on anywhere near as much.

Dave’s advice is to let the pump run and keep the vacuum up where the booster is the most effective. I told him I would heed his advice and leave it the way it is.

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February 8, 2017

Dave Lenzi’s vacuum switch arrived today so I installed and adjusted it. It is set to Dave’s instructions to turn on at about 16 inches of mercury and turn off at 18 inches. It all works but I don’t think I like the switch range because each time I use the brakes the vacuum pump turns on because the engine only produces about 15 inches at idle. I will email Dave and ask about turning it down a little. The one note is that I had to get a booster check valve and disable it in order to get a good tight connection to the booster. My straight 3/8″ to 1/2″ adapter leaked because it was designed for hose rather than the grommet that holds it in the booster’s opening.

I took the coach for another test drive after getting the vacuum pump working and it ran good. Not perfect yet but getting close assuming that the FiTech unit is actually “learning”.

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February 4, 2017

Last evening we were out in the street at our weekly Friday evening neighborhood meeting which is on our street but around a corner and out of sight of the house. I had left a note on our front door asking the Fedex driver to please leave the package containing the FiTech unit. The note contained the Fedex tracking number, my name, cell phone number and my signature. At about 5:30 or so a Fedex truck came around the corner from the direction of our house. I stopped the driver and asked if he had dropped the package as I requested and he said “no, I need a ‘direct’ signature” which means he needed me to sign his little hand held device. He even wanted me to go back to my house so he could drop the package there – I talked him into giving me the package out in the street – tight procedures for valuable packages I guess.

Anyway, there were no notes in the package and the only sign that something had been done was a small vacuum hose connected between the un-ported vacuum connector to the fuel pressure regulator on the side of the unit. I reinstalled the unit in the coach this morning and took it for a ride. It ran very well with almost no hint of any issues – almost because it did a little hesitation early in the ride but by the time I drove about 6 miles it was running very smoothly. I hope it is fixed – we plan to use it a little around town before taking it on a trip in about a month.

The replacement vacuum switch (the first one quits working sometimes) for my vacuum pump arrived today and I may try messing with it a little but I think I’ll just wait for Dave Lenzi’s switch to get here. 

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12:30PM, Friday, February 3, 2017

It turns out that UPS dropped off my unit at FiTech at about 9:39AM on Wednesday and then Fedex shows the shipment being ready for pickup at FiTech at 12:26PM, less than 3 hours later.  Cody, from FiTech, was supposed to call me yesterday with info about what was found wrong with it but so far, as of 12:30PM on Friday he has not. I did talk to him late yesterday and he assured me he would find out what happened and let me know. I called there this morning and talked to Bryce, another of the tech support guys, and he knew about the unit and that I was looking for answers. He promised to call me back but, so far, he has not either. I am thinking that it must be some sort of manufacturing defect that they saw immediately and corrected. Why else would they be reluctant to tell me?

Back to brakes. Dave Lenzi (he is an amazing designer and machinist who makes and rebuilds GMC parts) suggested that I reconfigure my vacuum pump setup to keep the pump from cycling and running unnecessarily. What he suggested is that the vacuum sensing switch should effectively be sensing the vacuum on the booster side of the check valve because, otherwise, a leak in the check valve in the pump itself will cause it to keep running. I made that change by removing the check valve from the booster port (Dave’s rebuilt boosters have dual ports) and replaced it with a 1/2″ to 3/8″ straight adapter, used 3/8″ hose to get to the vacuum switch, then back to 1/2″ for the vacuum check valve that was in the booster.  I am buying Dave’s adjustable vacuum switch and adding a vacuum gauge  (I got one from China for $5 on Amazon) so I can adjust it to come on at 16″ and turn off at 18″.  

4:45PM

I just got an email from Cody at FiTech that basically says that they could not find the problem. Says they put it on the test engine and “did not find a major fueling issue like you stated” but the put it on the “test bench” and ran a bunch of tests, burned new code into the ECU and then tested it again. It ran “flawless”.  If it ever arrives like it is supposed to tonight I will reinstall it tomorrow and give it another try.

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February 2, 2017

I have decided to try to actually use this section on my site as a log (blog?) of what is going on because I manage to forget when things happen and in which order. With this first entry of this type I will try to catch up on what has happened lately.

The FiTech mystery of today is why my FiTech throttle body is on its way back to me after being at the FiTech shop for less than a day. I sent it to them using an RMA and following all of their requirements like including a copy of my original invoice (I bought it directly from them?) and by filling out a standard form that Cody, their tech guy, sent me with the RMA#17-052 filled in. I sent it via UPS on Monday, it arrived at FiTech yesterday (2/1) morning and they sent it back to me today via Fedex. The only reason I knew it was on the way back was that I got an email message from Fedex. Cody did not know why they would have sent it back and he promised to call me right back but so far, 2 hours, has not.

I’ll go back a couple of weeks and recount what has happened. First thing was that from the very beginning of using the FiTech system I had a definite, measureable (1/2 second?) hesitation when hitting the gas pedal, especially when it was cold. Many times I had a hard time keeping it running at idle. I called FiTech many times (20 or so) and was told to try a lot of things like adjusting IAC Steps at idle, changing the ACC (accelerator pump) settings, and probably others. They asked if I checked for vacuum leaks, I could not find any leaks. 

It did turn out that my brake booster was leaking vacuum. I figured this out because my vacuum pump ran when it should not need to and with the engine stalled (happened quite a lot when cold) I had no brakes. I ordered a rebuilt vacuum booster from Applied GMC and a new vacuum pump from a guy on eBay. After a very difficult removal and replacement of the booster and the pump, the pump would hardly shut off because the booster was leaking ‘internally’. Applied replaced the booster with another rebuilt and this one actually failed while I was driving and I had no brakes a couple of times. I ordered a rebuilt booster from Dave Lenzi and I returned the second one to Applied. Dave explained what was probably going on and it involves the bracket that holds the master cylinder and the booster to the upper part of the dash. I am still working with Dave to improved the booster/pump configuration but my brakes work great now.

With the booster and the associated leaks fixed I still had issues with the FiTech unit. It was actually getting worse. One of the symptoms I could see via the FiTech Handheld unit was that the engine was running rich most of the time. A possible reason for this, according to advice and research, was an ignition problem – misfires. I decided that maybe my ignition module was going bad – they can fail in some mysterious ways and it is really hard to determine if it is fuel or ignition related. My fellow GMCer and good friend, Dan Gibb, had wanted a little tutorial on how that was done so I called him and told him my plan to swap the module on Saturday. 

On Saturday morning, with Dan watching and listening, I replaced the ignition module. It made no difference. The engine would hardly idle at all. With everything I knew to try exhausted I was drawing a blank when I thought of the perfect thing to try next – swapping his FiTech unit for mine. Dan agreed to give it a try – I had let him borrow my FiTech Command Center when his was not working so he was returning the favor.  We drove to his house, uninstalled his FiTech unit and installed it on my engine and all of the problems I have been fighting with the FiTech unit went away. It ran like a new car. We took it for a test drive and I could not believe how great it was. I tried it again on Sunday morning when the temperature was in the 40’s and it did not have any problems that were constant with my unit.

Monday morning I called FiTech. Cody answered the phone, I explained what was going on, and he sent me the RMA stuff. Below is what I sent back with the unit:

Problems:

• Does not respond to throttle – seems like accelerator pump issue if it was a carb – has been doing this from day 1 – vacuum gauge dips to “0” but no engine response for measurable amount of time
• Idles rough and sometimes stalls in idle – hot or cold
• Stalls and even backfires back through TB when throttle applied at low speed – cold
• Runs rich – has hard time matching target AFR – hot or cold
• These problems have gotten worse over time
• I have adjusted IAC Steps multiple times. Each time it has needed readjustment after driving for a while.
• I have restored factory defaults multiple times with no help.
• A friend has the same vehicle and engine with a FiTech 400 model (I am not using spark control) – we moved his unit from his vehicle to mine and all of my problems went away. It ran perfectly.

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GMCWS Logo

People new to the Classic GMC Motorhome are amazed about the amount of information and help that is available to them – primarily via the internet (GMCnet and now Facebook) but also via GMC clubs. All they have to do is ask a question and people are “crawling out of the woodwork” to help them. There is even a list of people who are willing to try to help people who are just passing through their areas with their GMC’s.

It is not obvious, so let me point out that the vast majority of that valuable GMC-specific information is available because GMC people (GMCers) have documented it – almost always for presentations at various club rallies. In fact, without the GMC clubs we GMCers would probably be like the owners of most other classic motor homes … mostly on our own.

GMC Western States, GMC Eastern States, local clubs and now GMC Motorhomes International (on June 1^st) make our technical information (developed as tech seminars for rallies, written for newsletter articles and recorded in databases) available to anyone who needs it. GMCMI will even make their online parts interchange database available to anyone who needs it – member or not. The only information the clubs keep as “members only” now is membership data.

Attending rallies is not the primary purpose of joining clubs – contributing to their support is. Running rallies, publishing data, and maintaining web sites costs money. Joining the clubs – the bigger clubs who generate and distribute the information, and your local club where there is lots of information, help, and friendship – supports those activities.  And to all you younger GMC owners, just remember, a lot of us may be senior citizens but, when it comes to GMCs, we are all still kids and, when we get together we cannot stop talking about our toys (GMC’s).

Carol and I belong to GMCMI, GMCWS, and GMCSJ (Saguaro Jetset – local to AZ and NM).  We cannot usually attend GMCMI rallies because they are too far away but we have managed three of them in our almost 10 years of ownership. We have attended all of the GMCWS rallies in the past 5 years and we attend most of the GMCSJ rallies each Winter. Our membership in GMCMI has always been to support the club’s mission in spite of our inability to attend most rallies.

Without your support, the clubs will not be able to continue developing, maintaining and promoting the new products and ideas that GMCers will continue to develop and present at rallies. Your membership fee supports the clubs’ missions – preserving and promoting the Classic GMC Motorhome. Join some clubs today.

Armand Minnie

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