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Username Post: Ram Jet 350 Constant Problem Child        (Topic#359773)
Posts: 2

Reg: 02-10-20
02-10-20 03:40 PM - Post#2786256    

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.


"16th Year" Gold Supporting Member
Posts: 1479
Loc: Chandler(it's a dry heat)...
Reg: 04-26-04
02-11-20 08:29 AM - Post#2786299    
    In response to travistodd1

I read your pain. But I have no help. My MEFI 4 runs great but I did have the ECM reprogrammed at a spped shop. I've never had any of your problems, but my just over 5500 miles is all to car shows. Hope someone else can help.

'56 3100 Short Stepside Someday
2001 Chevy Suburban 2500
2009 Saturn Vue w/20's

Member: Desert Classic Chevy's Inc.
Monty's 56 Truck
Avatar is my Truck

Posts: 724

Loc: Sault Ste. Marie, ON, Can...
Reg: 03-14-05
02-11-20 09:39 AM - Post#2786307    
    In response to travistodd1

My comments won't really help your diagnosis, but will just give you some more info.
I was picking up various pieces to build my own Ramjet; have the 350HO engine, ramjet intake casting, injectors, fuel rail, other misc pieces. I was looking into getting a TPI ECM and harness to run on this intake. It would be a speed density system, and use all the OEM sensors and computer. There was a fellow who built thse harnesses a few years back, think he was on the thirdgen site? maybe.
I don't have any experience with the Ramjet computer or its run issues.

Very Senior Member
Posts: 4638

Reg: 12-29-02
02-11-20 09:53 AM - Post#2786309    
    In response to travistodd1

Sounds like an electrical power loss. Check the truck wiring and ignition switch because a poor connection there powering the EFI would cause that.

Ultra Senior Member
Posts: 11441
Reg: 03-25-05
02-11-20 10:47 AM - Post#2786313    
    In response to travistodd1

I agree that it sounds like an intermittent electrical problem in the vehicle wiring. Most likely a bare wire rubbing a ground, shorting out the ECM power.

  • Quote:
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.

There should be a fuse in the fuel pump feed to protect the ECM.

66 Corvair (driving)
57 2dr HT (driving)
56 2dr HT (waiting to be restored)

Frequent Contributor
Posts: 2204

Loc: Lake George, NY
Reg: 11-11-15
02-12-20 08:17 AM - Post#2786360    
    In response to acardon

Are there any pending or history codes in the pcm.

Super Senior Member
Posts: 3845

Loc: Bedford, Texas, USA
Reg: 11-13-02
02-12-20 02:17 PM - Post#2786385    
    In response to Shepherd

Best thing I ever did on one of those engines was get an 0411
LS style harness, an 0411, a vortec 350 timing cover & crank reluctor, a vortec distributor and go to the LS based PCM. That engine has worlds better driveability with the later GM OBD2 computer. Terrible decision on GMs part to adapt a marine controller to run it for road use. I was able to start it and it was driveable on a stock 2002 van tune. Just VATS and Emission delete on the stock van tune it ran stronger than the GM MEFI4 ECM. Ran smoother, had better throttle response and got alot better fuel mileage. When the 700r4 died behind it, the owner swapped to a 4L80E and the 0411 ran it flawlessly.

1983 G20 Van, 350 TPI, Ported 906 Vortecs, Edelbrock 3817 Base, ASM oversize runners. Reed Custom Roller cam, 700r4, 12 bolt with 3.08 gears, Doug Thorley Tri-Y headers, true duals

Edited by 1983G20Van on 02-12-20 02:22 PM. Reason for edit: No reason given.

Posts: 2

Reg: 02-10-20
02-12-20 03:05 PM - Post#2786390    
    In response to travistodd1

I will be taking this to a friends shop this coming week to track wiring. I agree there is a short or ground somewhere causing the issue and I suspect it's a ground problem. I drove it to work and back yesterday and it seemed to be a little better. I will drive it again tonight and see what happens. Its a 45 minute drive each way up and over a 7,000 foot elevation so it gets a little bit of a workout. Hopefully it can be tracked down quickly, I have other projects I would like to work on.

Posts: 109
Reg: 05-04-03
03-06-20 09:08 PM - Post#2788104    
    In response to travistodd1

I ended up running my Ramjet 350 with an EZ-EFI 2.0. I'll see if I can find the writeup. I like it now.

Here you go, long story:

Edited by silvernblack on 03-06-20 09:09 PM. Reason for edit: No reason given.

Senior Member
Posts: 570
Loc: Lexington,NC
Reg: 08-28-00
04-01-20 08:14 AM - Post#2789979    
    In response to silvernblack

Did you ever get your problem solved?
I have a RamJet 350 in my wife's '62 Corvette and I also started with the MEFI3 system back in 2002. I also switched to the MEFI4 and have had no problems since, except for running very rich. I solved that problem by purchasing the MEFI tuning software from OBD Diagnostics and I now get 30-32 MPG on the highway. I have almost 50,000 miles on the car.

You mentioned that you had a "catastrophic fuel pump failure". Any chance that some debris from the pump may be clogging the fuel system or injectors? Have you checked your fuel pressure when the problem occurs?

Have any of the mechanics actually hooked up any scanning software to the engine?


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