Progress again on the '62 build....but first.
So spent the last two weekends working on the donor for the '53 C600, the 2k GMC 3500 has had issues running both before we bought it and after we bought it, the reason it has been parked for over 2 years has been a running issue which has been that it at times runs poorly. With only 124k on the clock unless it was something really odd it should have been a ignition or fuel problem, but it wasn't.
The Vortec 5.7L (basically just a 350 Chevy) still has a distributor, but does use a crank sensor for the EFI, the distributor not only distributes the spark to the correct cylinder but also acts as a cam sensor for the EFI. So when we got the truck it would start but had no power, checking the fuel pressure it was way low (20 psi when it should have been over 50 psi) so we replaced the fuel pump a few weeks ago which brought the fuel pressure up to the required 55psi.
This engine has what GM calls CSFI (spyder injection) which is notorious for problems with internal leakage, it's a pretty easy fix most of the time but a lot of work in a van, luckily it held fuel pressure for hours after being shut off which eliminates it from the problem list for now.
Replacing the fuel pump got the fuel pressure up where it should be but didn't really solve it's lack of power issue, at this point it could be a lot of things, low compression was pretty high on my list but there was no smoke out the exhaust, and the engine ran like it was being limited in some way electronically.
Then it wouldn't start again, checking it there was no injector pulse and no spark......
This is really getting weird I thought, when I plugged into the OBD2 connector there was no communication with the ECM, so I thought it might be a wiring problem, sitting makes it a prime target for mice to infest and eat the wiring (seen it before), but after hours of looking and probing the wiring found no issues.
So what is next? ECM itself was my guess, the ECM on these vehicles is located in a piss poor location both for servicing and actually having any real type of longevity.... the reason? GM decided that locating it under the brake master cylinder / hydro boost unit so any leakage from these items drips directly on the ECM, someone thought it was a good idea that in later years got moved over to the inner fender where it was out of harms way unless involved in a collision with the left front fender.....lol (how much could it have cost for the extra wire to put it inside the cab?)
It's a real pain in the ass to remove, lots of hoses in the way and the electrical connectors going to the ECM are locking which is a good thing until you want to disconnect them....lol
I got it out last week and with it on the bench removed a cover for the EPROM and look at what I found...lol
So yeah it's junk, been soaked in brake fluid several times and that has found a way into the unit, the aluminum casting was epoxy coated on the exterior but not on the inside once the brake fluid found a way in it was just a matter of time before it was going to die.
These types of problems are some of the most difficult to find until the ECM dies, there are so many different things that can become issues that seem to manifest then just go away that it will drive you crazy trying to diagnose the problem. I know that the original owner tried to get it repaired and the people who tried to find the problem just didn't know where to look at that time, like I said a failing ECM can cause a lot of unrelated problems that when tracked down are not the issue at all (lots of wasted time), strange error codes or codes that seem to come and go for no good reason, I hate trying to diagnose those types of problems for a customer, there isn't a winner even if you do find the problem because of the number of hours you spend figuring it out....yeah it is fixed in the end but the labor charges in a lot of cases really start to add up.
Lucky for us it died in such a way that nothing but the ECM could be the problem in the end....so I order a new ECM which took about a week to arrive. I had in the back of my mind that if this wasn't it we were going to have to look for another donor or just put a LS engine in it, I hate to make mistakes, my gut told me the problem was going to be easy once it was figured out, I kept going back to the mileage on the clock at that low a mileage it has to be something simple to fix, maybe not find, but fix...yes. Of course if the ECM was changed at any point in its life the miles on the clock could be wrong, when I ordered the new ECM I could have told them 80k instead of the 124k and the new ECM would display 80k on the odometer as long as the title hadn't changed hands to discredit that. (title shows more miles than the odometer)....lol
The new ECM has to be programed (flashed) with the VIN, transmission code, mileage, then when it's installed it has to relearn the crankshaft sensor counts and the passlock (anti-thief) code. It started right up with the new ECM, and once the Passlock info was learned (takes 30 min to go through the sequence) would stay running at idle, then it is a short procedure to relearn the crank sensor.... runs like a top now!
Sometimes in diagnosing stuff you have to be a detective and the more background info you have the better, we knew that this truck had been serviced and tuned up right before it got parked for several years, we were told it had running issues and the tune up was done to correct the issue which it did not...so it got parked.
When we bought it.... it ran, but poorly and lacked power, checking it out it had the low fuel pressure issue which we thought would solve its problems, but it did not. We now think that the ECM was the problem all along and the reason it got parked, the fuel pump was a casualty of it sitting for several years since it was not an original GM fuel pump and had already been replaced once in the vehicles life, at 124k that sounds about right for a fuel pump failure.
The whole thing with the truck was bothering me ever since we got the truck, I didn't want to get very far into that build not knowing if the engine/drivetrain was ok, and spent a lot of time thinking about what to do and what could be the cause.
So I felt it was better to devote the time to finding out it's issues and solving them before I went any further with either of the builds, now I can sleep better knowing what was wrong and that it is fixed, and we have a good donor for the C600!, BTW the ECM will be relocated in the build so it is better protected.... lol
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So with that out of the way and off my mind I can go back to the '62, yesterday I got the exterior of the drivers door stripped, spread a little filler on it, sanded, primed, and painted a nice minty green...lol
I hope to get that door hung next week then start on the passenger door, we plan to get the window gaskets soon and get the back glass and windshield installed shortly, then I need to prolly go back to the rear fenders on the bed and get them sorted out, the filler panels on the rear of the bed put back on, and it stripped of all the old paint, and the hood sorted out.... still lots to do! lol
Jon
