BLOWING 10AMP FUSE FOR BOOST SOLENOID

Boxcars

Banned
I was checking out some ignition modules to see it they were good and when I went into boost the car mildly backfired and after that I lost boost. My boost is set around 25 psi and now It generates only 10 psi of boost. I found the boost solenoid fuse was blown. I replaced it and it blew the replacement as soon as I went into boost. After this, I put on a different boost solenoid, went for a test drive, and it went into boost normally to 25 lbs. a couple times. I assumed it was fixed but when I went out again, it returned to the 10 lb boost limit with the same result -- blown fuse. Anyone know where I should start looking for the problem?
 
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Boxcars

Banned
Yeah, I remember over fifteen years ago I had the same problem on different TR and rather than tearing apart my harness I ran another wire to the solenoid and it fixed it. I can't remember where I ran it from, though. I start looking tomorrow. Thanks!
 

S10xGN

RETIRED!
Hey John,

Looks like there are several other circuits that might be the problem. Here's a diagram from the service manual, you could de-pin PNK/BLK at the C-100 connector and find out which side is shorted, then go from there...
8a-11-09.GIF
 

tlap

Member
I recently had this issue and found that my heated oxygen sensor, that plugs into and utilizes the EGR connector, was bad. When I unplugged just the O2 sensor from this circuit it quit blowing fuses.
 

tlap

Member
I recently had this issue and found that my heated oxygen sensor, that plugs into and utilizes the EGR connector, was bad. When I unplugged just the O2 sensor from this circuit it quit blowing fuses.
 

earlbrown

runs with scissors
Back in '99 I had this same problem and it drove me batshit insane trying to narrow it down. It always blew at the oddest times. I used that chart and unplugged everthing that fuse powers and could NEVER figure out what it was.

Then one day I was under the car behind the LF wheel and looked up....

Turns out the pointed screws that hold the steering column to the floorboard was the culprit. If you get under the car and look up, one screw is RIGHT AT a fork in the wiring harness. With just the right windage and a correct bump in the road the harness would kiss that screw and blow that fuse. My fix was to back the bolt out, cut off the point and reinstall it.

If your car is consistently popping the fuse when the solenoid is activated it sounds like you have a shorted solenoid. Have you tried leaving the solenoid unplugged for a while to see if the fuse stopps blowing?
 

Boxcars

Banned
Thanks for your reply. I also had changed to a different boost solenoid with the same result (blown fuse) before I posted here with my question. I had a similar short as you had described on your car. One of those screws you mentioned punctured my engine harness and shut the car down. It was totally dead and it took crawling under the engine compartment to locate the problem. It was shorting one of the fusible links that go to the starter. After I resolved the problem I rerouted my fusible link wires away to over the inner fender to a battery junction box. Anyway, I know exactly what you're talking about. I'll give it a look. I solved my boost problem by eliminating the boost solenoid from the equation. I just changed over to "tuner style" to adjust boost.
 

earlbrown

runs with scissors
Tuner style works just fine. Solenoids aren't needed for a conventional set up. ESP since we actually tune our cars and don't need the ECM to add boost for us.

That being said, tuner style starts to crack the wastegate open before you reach your desired PSI. A simple MBC can keep it completely shut until right before the desired boost. (that doesn't always mean a faster car if the faster ramp speed blows the tires away... but then again hi speed burnouts make me moist. :) )
 
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