Wanted: someone to test a 1227727

[JeepsAndGuns]

I bought a 7727 from the junkyard as a possiable swap for my 4.0 in my jeep. I was wondering if anyone here could hook this thing up to something and make sure its good. I pulled it from a 92 grand prix with a 3.1, and it has the factory memcal. Just wanted to make sure its good before I go too much further with anything else. I can box it up and mail it to you, and you just mail it back in same box.

[1project2many]

There aren't a bunch of things I've seen go wrong with the 7727's. Quad drivers would fail and those would set codes. I've seen a faulty power board before which caused random resets. That's probably just loose solder connections. And I've seen the CTS input bad a couple of times but I think those were due to coolant wicking up the CTS signal wire.

IMO if you're using it for a project go ahead and proceed expecting the ecm to be ok. If you think you have a problem I'll offer to send you another ecm to use. If that fixes the problem you can send the questionable part back here and it will be my problem. I would offer to check yours but all I have is a test bench and that's not even close to a real automotive environment.

[EagleMark]

I'd agree, use it and see if it has issues, robust units and probably cheaper to but another JY then ship around.

[dave w]

Once you get the '7727 harness built, you can basically bench test the '7727 yourself. Most of the functions can be tested, but not all the functions. Basically hook up everything up electrical, apply power (both battery +/- and ignition on) and spin the distributor with a variable speed electric drill. I use one spark plug connected to the coil to test for spark. I connect a laptop to the ALDL connector to data log. I have a hand vacuum pump connected to the MAP. I use noid lights on the injector connectors. I use a heat gun to warm up the CTS and MAT. I move the TPS by hand and watch the data log screen to the TPS% / TPS voltage change. I use a test light to check the fuel pump relay. I can't test O2 volts or VSS. I've been lucky so far, when the '7727 passes all the above test, the engine will start.

The video is me testing a TPI '7165 ECM (no VATS).



dave w

[droptopstng]

hey jeeps im in oxford if you wanna make a run up here im sure we can go guiny pig someones car around here lol

[EagleMark]

It really is easier building the harness and entire system on bench testing all parts of system on bench before installing in the car.

Here's a show off picture with one system running off AutoProm via a drill on the manifold while recording data, one system running a ECM on a JimStim, osiliscope checking injector circut and and Scan tool checking the other system... I was bored...



Here's the drill drive for distributor to intake down the side of bench, makes it easy to lay out harness. I have a mount for bench in front of intake to drop distributor in for building a front distributor harness.




And how it looks today with the harness I'm working on.


But I just don't have a harness to hook up to your ECm or I'd do it. But you'd still be better off doing it all on bench and then doing the install. Since I started doing them this way everyone has fired up without issue ready to drive and tune.

[JeepsAndGuns]

Cant really do the test bench, as I dont have a complete harness. The ecm I got I just grabbed about a foot of the wires coming out of it and thats all, the rest of what was in the car was hacked up bad from someone removing the intake. I will be basicly reusing the current harness already installed in the jeep, hooking up where the old jeep ecm connector is, and running new wires only where needed.
Since it sounds like these are pretty togh ecm's then I will just hope for the best. What I may do is next time I am at the junkyard is pick up another one to have as a spare.
Thanks for all the suggestions!

droptopstng, this undertaking is still a month or two away, I may have to come down one day. Would be nice to chat with another tuner.

[droptopstng]

well if you would like come on but im telling you im no tuner just a tinkerer lol but come on anytime you like

[S3TPI]

Still need it tested?

[JeepsAndGuns]

I just got done making a test harness like the guys showed above. I plan on putting it to use this weekend test them out. I have already tested a 7730, so I know my harness is good.
Thanks for the offer.

[JeepsAndGuns]

How did this post end up in here? It was in the for sale/wanted section.

But this test harness has turned out to be a handy project. It started life as a hacked 7730 tip harness. I replaced the missing plugs, straightened it out, ran all my power and ground wires to some clips, then cut and spliced in plugs for a 7727, and 7427. Now I can test any of those 3 ecm's with the same harness. I have a coil hooked up and used a distributor to test the system. I simply held a large gauge ground wire aprox 1/4in away from coil post and watched the light show..lol

Today I tested the 3 7727's I have, found 2 were fine, and 1 was bad. Its already starting to pay off! I then pulled the IAC and MAT from my jeep 4.0 to test them. Found the MAT has incorrect ohm range, and found the correct pinout for the jeep iac. It has the same 4 wire flat connector as lots of the gm ones, but its obviously wired differently. I hooked it up with the gm pinout and it wouldnt work. I compared the diagrams from the jeep and the gm and hooked it up how I thought it should be, but still did not work. Tired a different combanation and it worked backwards, finally tried it another way and got it working! Wrote down the correct combo.
Next I plan seeing if I can get the jeep speed sensor to work.

[EagleMark]

I moved it as it seemed a strange thread in clasifieds?

Great work on testing Jeep sensors! Dosen't $8D have some VSS scalers to adjust if Jeep is differant PPM?

Cool doing work on bench and testing things before install on vehicle, isn't it? Man it has saved me tons of time while much easier to work with. All installs since doing it this way have been turn key run, no error code!

[JeepsAndGuns]

Yea, if I hadnt been able to test the IAC and find the right pinout for it, I would have just hooked it up on the jeep based on what I thought would be right based off the wiring diagrams, and it wouldnt have worked. Man that would be a headache trying to fix it then!!
Found out the CTS also has the wrong ohm readings, however the jeep CTS is identical to the gm one, same thread size and all, so it will just swap right in.

The jeep vss is 8ppm, and the 7727 8D looks for a 4ppm, I think robert said I can raise the road speed constant. However, the 7727 vss is magnetic, and the jeep one is hall effect. Robert also said I should be able to install a capicter and be able to use it, so I am gonna try that. Having the test harness will allow me to do so before I even touch the jeep.
Gonna try and work out as many kinks as I can before I install. And although I am pretty sure it will work fine, I still need to test the TPS, I just dont have a spare plug for it, and the pins/connector are completely different from the gm ones. Jeep already uses a gm MAP sensor...lol