"The white truck" My 89 V3500 **DRIVING IT

[MTBLAZER89]

Popping the ECMB fuse usually means there is some kind of a short in the fuel system wiring. I had the same problem on my V3500 Crew Cab, and it turned out to be a fuel pump that died and was shorting out internally.

This is a new pump.

 

[ZooMad75]

Jump up on the fuse. I know it sounds like a hack way to do it but follow along with me.

I had mine pop the ecm-b fuse (LS swap, but the fuse was still in play as we used the stock fuel pump relay). I was on the highway heading to rescue my wrecker driver who got himself stuck in the snow. Anyway doing my roadside diag I discovered the fuse popped and threw in one of the same size from the radio. It was 10 or 15 amp IIRC. That got me home. But driving it to work it did it again. So after talking to one of my techs at work he gave me a fuse buddy to monitor the load on the circuit and see what it was actually pulling. The fuse buddy is a pretty trick little device in that it plugs into the spot where the fuse goes, has a good length of cord to the actual item with the amp display and a spot to put a fuse into so the circuit is still protected.

What I found using the fuse buddy is the amp load never really spiked to pop the fuse, but the load was right at the rated limit (within an amp) for the length of my drive and in that time the fuse would pop. I got down to the point I could tell it would happen within 35-40 minutes of driving it. I noticed the fuse didn't have the normal black spot where it popped, but a good chunk of the fuse plastic was melted from heat. After discussing it with my tech he suggested to bump the fuse up 5 amps to give it a little margin of safety. I did just that and left it in the fuse buddy for a couple more drives and while it never exceeded the original rating, running a few amps below the fuse rating kept it from popping. I ended up just running the larger fuse and haven't had it pop since. I know based on watching the actual load that if the circuit spiked like in a short to ground the fuse would still blow like it's supposed to, but it's not too high to end up having the wiring be the fuse and catch the truck on fire either.

I keep the fuse buddy in my tool bag as it's way easier to use to track an issue on the fly that breaking the circuit open to run meter in series since I don't have a clamp meter.

 

[MTBLAZER89]

Reason for fuel leak.

 

[MTBLAZER89]

I'm going to try and drive this thing around a little today. I found a bare wire, but it was just the fuel gauge wire so no joy there.

I added some wire loom to some areas where contact with metal could happen, but couldn't find anything that would pop that fuse. I started it and went through and bent and pulled on wires and couldn't make it pop. It's started several times without issues.

As an emergency backup I added a toggle switch to the fuel pump test lead so I can force the pump to run if the thing dies in the middle of an intersection or something. God knows I can't push the thing by myself. #hackjob

 

[MTBLAZER89]

Well I made it to the gas station and home without any drama. The exhaust leak is terrible. Pretty sure the engine has a tick, but it's hard to tell. Temp stayed solid at 200 and 35 lbs of oil pressure at idle. Ran ok, but man this thing is a turd. At least it looks cool. 5 year old rattle can needs some love though.

 

[skunked]

The phat block will be a huge improvement but I'd wait til the K5 is up and going.

 

[MTBLAZER89]

The phat block will be a huge improvement but I'd wait til the K5 is up and going.

Its already got a phat block, but something isn't right.

Yeah as long as I can keep it running as is then I can use it for Spring projects as needed without getting tearing things apart. I'm getting pretty close to throwing the engine cage/exo on the Blazer so it's moving along.

 

[1-ton]

One place you could look for wires that are worn through is on the left side frame right where the frame curves under the cab front door. These are the wires that run to your fuel tanks and tail lights. Chevy square bodies are known for wiring to rub through in this area.

 

[MTBLAZER89]

One place you could look for wires that are worn through is on the left side frame right where the frame curves under the cab front door. These are the wires that run to your fuel tanks and tail lights. Chevy square bodies are known for wiring to rub through in this area.

Yup, I threw some of that 1/2" plastic loom from the body mount up to the wire harness there. Its so tight to look closely down there, and evrything is dirty and oily so it's hard to tell. I will be able to get a closer look with the engine removed.

 

[imiceman44]

Yup, I threw some of that 1/2" plastic loom from the body mount up to the wire harness there. Its so tight to look closely down there, and evrything is dirty and oily so it's hard to tell. I will be able to get a closer look with the engine removed.

Yeah at least you will make sure the next engine doesn't suffer from the same problem

 

[MTBLAZER89]

Yeah at least you will make sure the next engine doesn't suffer from the same problem

Yeah! I enjoyed driving it the short distance today. I look forward to having it as a useful vehicle again.

 

[MTBLAZER89]

I've taken three loads of scrap metal to the yard in the last two days. Haven't had a single problem so I'm betting it's the area where the harness curves under the firewall by the inner fender there and putting that wire loom on "fixed"it. It's actually running ok too. Still a turd, but idles and drives fine. My side yard and trailer are actually visible now.

 

[swettysblazer]

I'll bet money its on the oil pressure sensor on the back of the motor. I was popping the ECM B fuse consistently when wheeling, and I found that the wiring was rubbed through on the pressure sensor pigtail when the truck was flexing and shorting out on the body and popping that fuse. I would start there.

 

[79rustyk10]

Did you get the surging idle sorted out? Having the exact issue with the TBI350 in my 79.

 

[Kay86K5]

Did you get the surging idle sorted out? Having the exact issue with the TBI350 in my 79.

Try replacing the IAC (Idle Air Control) on the side of the throttle body. I had that happen on my TBI350 I swapped into my K5, and it ended up being that. And seen many others with similar symptoms that ended up being the IAC. They're cheap and easy to replace

 

[MTBLAZER89]

I'll bet money its on the oil pressure sensor on the back of the motor. I was popping the ECM B fuse consistently when wheeling, and I found that the wiring was rubbed through on the pressure sensor pigtail when the truck was flexing and shorting out on the body and popping that fuse. I would start there.

Guess I forgot to update this! It seems to be a wire that runs between the inner fender and firewall to the rear of the truck. Replaced some loom and the fuse quit popping.

Did you get the surging idle sorted out? Having the exact issue with the TBI350 in my 79.

Try replacing the IAC (Idle Air Control) on the side of the throttle body. I had that happen on my TBI350 I swapped into my K5, and it ended up being that. And seen many others with similar symptoms that ended up being the IAC. They're cheap and easy to replace

I replaced the throttle body with another I had so I would assume it was a vacuum leak or the IAC in the other TB. It runs pretty ok now with the exception of a terrible manifold leak. Hauled 6 yards of garden dirt (2 yards at a time) and 3 yards of pea gravel for some yard work.

 

[swettysblazer]

Fuel pump wiring possibly then

 

[MTBLAZER89]

Fuel pump wiring possibly then

Yeah I am sure it's the hot wire to the selector/pumps where it passes under the firewall. I'll likely pull the front clip when I swap motors so I will fix it then. Impossible to get your hands in there with the inner fender installed.