Woosh,Looks to be sold a long time ago for quite a lot.I and all of you guys gotta wonder how its doing today. No? The ad makes not only the Cad swap no big Whoop, but EFI to boot! Really? Gary,any other GMC'ers http://www.gmcclassics.com/leonard_coach/
That coach was built with a 403. Wonder how that Accel sequential port injection is working? I have tested that EFI equipment on my 79 Eldo, had some issues with the ECU. There is more advanced stuff going on the GMC list. Bruce Roe
Hi, I'm new to the forum. I bought this GMC motorhome, and drove it to Texas from California. It had a partially clogged injector that made the #1 plug white and the rest dark brown. Getting into the program and increasing the duty cycle of this one has brought all the plugs to a uniform light beige color. It had 21 lb injectors, and I bought some 24 lb "flow matched", don't I hope, used injectors, have yet to install. It runs very well, but quickly heats up in hot weather if you put your foot in it. Idles not so well. I see inside the valve cover some new valve train components, the aluminum rockers and a solid rod fulcrum. Has a stumble off idle, you have to watch it if you don't want to spin the tires. Stalls once or twice when cold. I will get into the Cal 7 program to see if I can change this. Since it is new to me, I am having to be methodical in checking everything that has been done, as information is sketchy. More later if you are interested in this one. Sending oil analysis tomorrow, as the oil appeared to lose viscosity. It still runs very well, has great potential, I think. It has a wide band Oxygen sensor, I believe.
cbryan, There were no GMCs built with fuel injection, but a lot of people have worked on converting them to Olds 403, 455, or Cad 500 fuel injection. So your equipment is a custom job. One group that is dedicated to the GMC EFI is called GMCMH, you might want to join them. There are others dedicated to GMC motor home support. Bruce Roe
Thanks, Bruce, I have checked into the GMC motorhome forum and see that most are now running the GM throttle body setup from the '90s, with advanced users who are working on a lean cruise, but I am not monitoring their work. I have my own problems and opportunities with this setup, I think. I thought you might be interested in my adventures with this ACCEL aftermarket system. I, on the other hand, would be interested with the problems you had in your ACCEL installation. Don't want to do the impossible or spend loads of time trying. I was so surprised to see my new motorhome written about. A few people say I have gotten a good deal, but there is a punch list of about a foot, some not trivial. Mostly requiring concentrated effort to get a quality outcome. Thanks again, Carey
Care, Yes I would be curious how your system is configured. My own interest has been to upgrade the 70s Cad fuel injection systems still driving around on Olds 350 & Cad 500 engines. And convert from batch to sequential injection in the process. I don't know how many cars are out there, but I get about an ECU a month for repair. I keep the original port injection fuel system, just change the electronics, make a custom wiring harness. An ACCEL 7 77022 claims sequential & ability to drive peak & hold injectors. Like all after market engine electronic systems I have purchased in recent times, there were bugs. It would not put out the peak & hold waveform Cad injectors need. Instead it had some kind of oscillating current limit I find unacceptable, but I could add an external fix. The power to the idle air motor didn't shut off in certain circumstances, causing it to overheat. There were other issues I forget right now. I mentioned to the factory getting the software fixed. They said they would be glad to load the latest for $300 (to make it do what it was supposed to do in the first place). I worked around the bugs instead. Bruce Roe
Bruce, I recall reading some flaming posts about the idle motor and lack of ability to even recognize Cadillac firing orders. Send money to Accel and they will send some fix. When fix didn't work, send system, and they return it, not fixed. Send money and they finally fix system or just part of the system. It wasn't confidence inspiring, but on the other hand, I had a runner with this system, with money already spent. So now, I read that there are two hardware keys with an advanced one to change all parameters, add money again. The cheaper hardware key does not apparently allow all parameter changes needed. I am interested in cutting off injectors on coast, etc, after I get it dialed in and operating well and fuel mileage documented. I am going to check very basic things first to make sure I don't have elementary troubles like manifold leaks, engine mechanical troubles, firing order, TDC set inaccurately, voltage drop, bad engine grounds, etc. On Accel, I am aware that so many things can go wrong with such a complex system, and I don't hear about distributors dying, electronics smoking, or many other things. There are people like Rance Baxter who are having some good luck with this system, I have contacted him and he seems to think I am working with something worthwhile. If Hubbell space telescope designers made mistakes, I can forgive those who are working on something with so much promise. Thanks for answering me, I will post progress and my specific setup. I am short of documentation, don't even have the cd or dvd, and understand documentation is sketchy at best. The reason I think I have a wide band sensor for example, is that I found a wide band sensor boxtop in the box of spares. Not too scientific. Keeps me out of the karaoke bars. Carey
From personal experience: Accel DFI is shit. Stay farrrr away from this train wreck of a company. :twocents:
EFI on GMC Carey, I think the ACCEL can be made to work. Perhaps you have high impedance injectors, OK. Are you running port or throttle body injection; the old Cad 8 injector system only fits SB Olds or BB CAD? Whose distributor, is there electronic spark mapping? There are so many EFI systems out there, I can't keep a handle on them. They are very poorly specified for features; talk to user groups for that. Poor quality software is my biggest problem on everything I buy. I set them up with a simulator on the bench. I can set up any situation and watch with my scope, much easier to identify bugs than tripping over them with a smoking engine. I have a 77022, likely documentation is pretty similar for the VII series, what do you have? The distributor still controls plug firing order; it is wired into the injector pins for sequential injection. Unless you have coil packs, like my tractor. For my time and money, there is more to be gained with a programable advance curve + knock retarder (per cylinder is best) and keep the carb, than the other way around. I have my doubts about the fuel cutoff benefits. If you lose inertia via additional engine braking, you have to put it back with 4 times the gas (25% engine efficiency). A WB OX sensor will have at least 5 wires; a narrow band usually 1 to 4. Bruce Roe
Bruce, Thanks for responding. It's a dual sync distributor. I have to do some bus work tomorrow, safety for the kids, so won't get to look at the MH setup. All plug wires by Accel. Has the stock Cadillac iron manifold drilled for 8 injectors. Sequential. Each injector can be modified with respect to duty cycle. Will check on the numbers but I think hardware is about 2003 or so, and software has been updated. Accel coil mounted under front seat in inside of motorhome, along with the computer, flopping around in there, not mounted. It tells me that perhaps the previous owner was trying to get it to run correctly and never buttoned things up because it was never to his satisfaction. I don't think he has mounted a knock sensor. Now thinking about engine issues. I just got back the oil analysis. Blackstone says no apparent problem with oil overheating despite the absence of oil cooler, viscosity was not bad at all. However, there is evidence of iron, copper, lead in the oil pointing to crankshaft bearing issues. Now, after changing the oil and filling the filter 2/3 full of new oil, there was about five seconds with no oil pressure, after which it came right up. During that time, there was no main bearing or rod knock I could hear at all. (I remember previous engines with loose or bad bearings were noisy during that time.) Used Rotella 5w40 synthetic for the fill. Interestingly, the lower oil pressure at idle with the slight noise is gone with the new oil. Older oil (PO says Mobil 1 but didn't state the viscosity.) was only 2000 miles old, but I wanted to see about the analysis. Puzzling to me. Got the noise at ldle at 23 lb pressure when hot. Now, with new oil, the hot idle pressure is more like 35, with no noise. Hot cruise pressure is now 50 lb like when I picked up the MH, but after some hours of hot weather driving, it went to 43 and deteriorated slightly from there. Coolant temperature stayed at 180 most of the time, always caught it before it got to 200 and got my foot back out of it. It ran so well at speed that it was hard to go the speed limit. It's a willing runner at cruise, anything off idle, throttle response is fine. Problem only with cold start, stumble coming off idle. Mechanical oil pressure gauge, VDO. The magnetic oil plug had only one whisker of metal filings on it when changing the oil that I could see. It might be completely all right, but the lowering oil pressure cured by an oil change is puzzling to me. No other issues reported by Blackstone, they want another sample at 2000 miles additional. I will probably do it. Idle is still not smooth, this is a Cadillac, after all. Not a smooth idle. It had the torque cam, which I think means it should idle fine. More later, it's been a busy week at work. I will try to get ACCEL numbers if I'm not fully tuckered out tomorrow afternoon. I understand what you mean about cutoff of fuel during deceleration. I didn't think that through. Thanks. Carey
If they used the original Cad 500 injectors, they are low impedance with a blue band. They are a big 49 lb/hr, because the original Cad system limited the duty cycle to 50% (every other crank revolution). The smaller 39 lb/hr Cad green injectors are plenty for sequential injection, which can go to 85% duty cycle. But many people put in high impedance injectors. If you are saying they made an EFI intake by drilling a carb intake, that is likely what you have. Bruce
Bruce, Thanks for your reply. Yes, that's what I have. Ford 460 injectors mounted on a drilled manifold. Originally 21 lb/hr but I bought 8 of the 24 lb/hr injectors that have four spray holes. (Still uninstalled) . Flow matched, so they say. Got all the seats reupholstered needing it on the buses, replaced a turn signal cam, cleaned connections, greased all with lubriplate 105, and all is well. Also reset stop light switch which was not turning off all the time after the bus was parked. May check out the ACCEL particulars later today. Best, Carey
Holy Crap Carey,Are you saying the coach that is in the Ad is the one you got?If so I would get a proper quadrajet on for another long trip.Way to nice a machine to have trouble on the side of the road. :twocents:
Based on my 403, I'd estimate the 21 lb/hr injectors running up to 85% duty cycle, will max around 4200 rpm on a 455. 24 lb/hr should go 4800 rpm. Sometimes people change the pressure, to change the numbers. Bruce
After hearing more of the particulars of your situations, I must again advice you: run far, far away from that Accel system, if reliability is a goal. :twocents:
Hi, folks, After seeing yet again the suggestion to run, not walk away from the Accel EFI, I plan to keep with it. It is working at present. Recent discovery is the acceleration enrichment system that was actually set leaner for the warm engine. I enrichened it and soon I will know if it helps the off-idle stumble. I got some help by boosting duty cycle for one injector that wasn't flowing as much as all the rest. It is working well. I think it needs some help with cold starts, haven't found that parameter, but everything seems to be working well. I just worry about what happens if something goes wrong on the road. Wife will not be a happy camper if so. It appears that whatever is wrong has to do with lack of development and understanding on my part. It's fun going on with the process. I plan to be careful to make sure the power enrichment system is operating to protect the exhaust valves. If indeed, I have to change this out for a GM throttle body setup with all GM parts, then that will be a pretty big job. Have to talk myself into taking this out, and in the meantime, I am putting more and more into understanding this system. I have learned a lot from the GMC MH forum, enough to know that I am aware of more gaps in my knowledge than ever before. Thanks to everyone for their kind help. Carey
Glad to hear from you again. My thought on the ultimate reliable system, Use a Qjet as the throttle body for your port injection system. If the EFI fails, pull the fuse, turn on the gasoline to the Qjet, and go. I can do the ignition too. Install a crank trigger system. If it fails, just move 12V and your plug wires over to the HEI you were using to turn the oil pump. I actually did this on my tractor; the "lawn mower" fixed ignition timing engine ran far, FAR better with an electronic ignition timing map. Bruce Roe
