MAP Adjuster Issue

[NelsonATC]

I have gotten to the point with my build where I have now installed my map adjuster.

I am using the adjuster from Lehigh. I wired the adjuster into a 2- way toggle switch So that I can switch from stock voltage, to the adjusted voltage without rewiring. When I switch to the adjusted voltage, which at this point I have set identical to the stock voltage (5v), My engine sputters, and struggles to stay at idle, stalling frequently. When I switch back stock voltage, everything runs fine. A quick check with my multimeter shows that when I switch to adjusted voltage, the input voltage drops from 5 with the ignition on, but not running, to 2.5v when running.

The wiring is correct

Any thoughts?

[Cheromaniac]

Can you post a photo of the wiring?

[NelsonATC]

Won't be able to take any picture for at least a day or so. I have checked the wiring time and again and it is correct.

I cut the 5v feed to the map, ran the output from the adjuster to the map,grounded the adjuster (I have grounding bars that run direct to the battery, so my grounds are solid), and tied into a 12v feed (on my cj, it was the old clock output of the fuse box). I took the original 5v feed to the map and attached to a SPDTswitch along with the adjusted voltage feed so I can toggle back and forth from stock to adjusted. The lead feeding the MAP is the center pin on the switch. The adjusted and original 5v feeds are the outer 2 pins.

[Greenneck]

I tried build one of these myself and am having the same problem so keep us updated

[Cheromaniac]

Here are the schematics of my homebrew MAP adjuster with and without the SPDT toggle switch:




Hope they can help you troubleshoot the problem.

[NelsonATC]

The first pic is exactly how I set mine up.

The confusing piece is that I have 5v (as its set now) from the MAP adjuster, but on e I flip the switch to send to the MAP sensor, voltage drops to 2.5

[Cheromaniac]

on e I flip the switch to send to the MAP sensor, voltage drops to 2.5

Don't flip the switch while the engine's running. If you do, that could be the reason.

[NelsonATC]

Did not know that. I will try switching over with the engine off and report back.

[NelsonATC]

Haven't gotten to this. Too GD hot here lately and I haven't had they desire to dig into it. Hopefully Sunday when things cool down.

[Cheromaniac]

Too GD hot here lately

It's 115*F (46*C) where I am at the moment.

[NelsonATC]

Ok, here are the labeled pics for my wiring:





Just a change from my previous statement, when the ignition is on, running or not, the voltage drops to 2.5. If it is on and NOT running, voltage continues to drop. When the Jeep is RUNNING, voltage stays at 2.5. If I attempt to adjust the output at the MAP adjuster, it jumps up to 2.6, but quickly settles at 2.5v.

I took the MAP adjuster off and tested it. It seems to be working fine, adjusts as it should when hooked to a 12v source. I also bypassed the switch during a test, so the switch is not the issue.

I thought it could be a 12v feed issue, so I hooked straight to the battery, with no changes.

Tested all wires for continuity and shorts, no issues.

I tried the switchover with ignition off, as suggested, no change.

I'm stumped

[Cheromaniac]

Υour MAP adjuster appears to be correctly wired but I think I've found a problem with the wiring to your switch. What are those two green wires going to the middle terminal of the switch (see white rectangle in attached photo)? The only wire that should be coming from there is the adjusted voltage return to the MAP sensor.

[NelsonATC]

There is only one wire going to the terminal, if you look closely, that wire is just lying over the top when I took the picture. It's an optical illusion

[Cheromaniac]

Oh well. I don't know what else to suggest right now but something's definitely wrong.

[NelsonATC]

Here's hoping that someone who has had this issue sees this and can help!