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Discussion Starter · #21 ·
I need to climb up under the hood to take another look to verify the distributor.

The timing was an issue. I had the heads rebuilt, and forgot to mention the correct procedure for setting the timing to my mechanic. That caused all sorts of problems but once the little light bulb came on it was a quick fix.

The Blazer is running very well other than this little stumble issue. It only does it once or twice during my 45 minute commute and is barely noticeable. Probably more noticeable to me because I know its doing it.
 

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If you have the 8 pin HEI that I referenced in the photo, then Pin B on module needs to be unhooked when setting the timing. By unhooking that wire it eliminates the ECM control over the ignition module. In factory setups it will be either a tan wire or a tan wire with a black tracer. Also, the factory had a connector inline that was designed to be unhooked for this purpose only. It was on the firewall in the C/K trucks under a black plastic cover.

The manual that lmsport attached is very helpful.

If you do have the 8 pin, then the comment that 70bossranchero mentioned that you need a tool to set the timing is not accurate. You don't need a tool even though there is a tool that will work also, basically, there is more than one way to skin a cat.
 

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Since the OP said that he has the tool, and an MEFI 4 doesn't have a plug to disconnect the timing control. Then using the tool for him would be the easiest route. Alternatively, if he didn't have the tool, than I would have told him to jump the diagnostic plug with a paper clip, which is way easier than trying to remove the timing control wire from the distributor connector. I didn't mean to imply that the tool was the only way to set the timing, I was bringing up the fact that there is a special procedure for setting the timing, which no one else had mentioned, and obviously his mechanic was not aware of.

Sent from my moto x4 using Tapatalk
 

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New to the group and hoping someone with some expertise can help. This is a long post but I wanted to provide as much information as possible.

I have a Chevrolet K5 Blazer I have set up to be my back roads vehicle. When I purchased it, there was already a Ram Jet 350 installed. This engine is slowly driving me insane. My current battle with it is I will be driving down the road and it will suddenly and momentarily cut out. It continues as if nothing happened but it is very dis-concerning. I have replaced the ECM in the truck and it did this prior to the ECM replacement. Once in a while, it would turn off completely but would restart.

A little history on the vehicle...

Engine was installed several years ago and started out as a MEFI 3 but was converted to MEFI 4 prior to my ownership. Unfortunately, it set for a very long time before I purchased it.

After purchasing, it was doing some strange things and ultimately I replaced the IAC, MAP, MAT and O2 sensors. This made it run much better.

At one point, the heads were rebuilt. After the heads were rebuilt It ran great but it started to develop this cutting out issue.

One day, going to work up in the mountains, it cut out completely and would not restart. I am unsure if this is related to the original issue. Prior times the engine had cut out but the fuel pump would still keep pumping and the Bazer would easily restart. This time I noticed the fuel pump was not engaging at all. Further inspection revealed the fuel pump had a catastrophic failure, shorting out my ECM.

The fuel pump was replaced with an Aeromotive A1000. A new ECM and complete Ram Jet wiring harness was installed. The Blazer continued having issues. At times, I would be driving down the road and the Blazer would backfire out the exhaust. Often, the Blazer would enter into some type of safe mode and reduce the engine performance severely over 3,500 RPM's. I am unsure if the limp mode caused the back fire or vice versa. There was not always a back fire but it would go into limp mode pretty often. This was after the green mode had passed.

I discovered the shop who installed the computer and wiring were unaware of the process to correctly set the timing. That issue was addressed and the Blazer runs much better but it still will cut out going down the road.

It does not run hot. I have never had overheating issues. I am at a loss and unsure what is taking place. I have spare sensors I keep just in case there is an issue on the trail. Changing out the various sensors makes no difference in the way it runs.

Any ideas? Thanks in advance.
On my Ramjet If I turned a slight right it would bog down or die. But would always crank back up. Then I noticed it only did it under a quarter tank of gas. It's in a 37 coupe so small 12 gallon tank. But since I keep it above a quarter tank it hasn't done it in over 6 months. You may not have the pickup low enough. Try running with 1/2 or fuller tank an see if that helps.
 
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