Jeep cherokee with MSII No RPM

[eluis]

Hello to all.
I recently bought a MSII 3.0 assembled from diyautone to install in a 1988 Jeep Cherokee laredo 4.0l. They are helping lot.I writting here to share with all and to be part of the forum.
The issue that I have now is that there is RPM signal from pin 36. I am using the stock crankshaft sensor, the ecu had the jumpers for VR sensor and I loaded the BG code to trigger crakwheel. I will apreciate your help.
Att. Eluis.

[eluis]

Sorry, I had wrote before that there is RPM. And the problem is that there is not RPM in megatune and no pulse from Pin 36.
Excuses to all.
Thanks.
Att.Eluis.

[Bernard Fife]

eluis,

What code are you running? Have you loaded code? Does it work on a stim? Have you checked the troubleshooting steps here: http://www.megamanual.com/ms2/V3trouble.htm?

Lance.

[eluis]

I loaded bowling& Groppo code 2.88. I all ready set the ECU type to 1 under fuel set up. I can see all reading and set the wheel decoder setting like these.
21 base teeth
1 missing tooth
21 skip teeth
12 delay teeth
Thanks.

[Bernard Fife]

eluis,

For a 6 cylinder - 4-stoke engine, you need 3 tach teeth per revolution. And there must be actual physical teeth at these locations.

If I read your post correctly, you have 21 teeth, one of which is missing (so 21-1). Skip teeth is the number of teeth between tach teeth, so 21/3 = 7.

Delay teeth depends on where you sensor is located relative to #1 cylinder's TDC.

There's more here: http://www.megamanual.com/ms2/wheel.htm

Lance.

[eluis]

Ok Lance I will check how many teeth has the flywheel. But last monday I was seeing another flywheel that I have and I think that the flywheel has 3 places with missing teeth, and what I saw in the MSII trigger wheel information the trigger wheel only has missing teeth in one place of the wheel. But I am not really sure. I will going to check again and I will let you know.
The wheel decoder setting that I wrote before I recieved from Matt. of DIYAutoTune. He is helping me to.
Thanks.

[eluis]

Hello Lance here it is some information about the Jeep flywheel.

[Matt Cramer]

Lance, the settings are a bit of "code abuse" I came up with a while ago after noting that the wheel decoder would accept settings that would only yield one tach tooth per revolution. So the idea is to make the wheel decoder handle three missing teeth in a revolution. It may need to be treated as having 22 base teeth and 2 missing teeth.

[Random Hero]

I'll soon be building an MSII for my buddy's Jeep 4.0, isn't there also a position sensor in the distributor?

[Matt Cramer]

I'll soon be building an MSII for my buddy's Jeep 4.0, isn't there also a position sensor in the distributor?

What year 4.0? Most of them have just a one tooth wheel with a Hall effect sensor.

[Random Hero]

94

[Matt Cramer]

94

That year would have three clusters of four teeth each on the crank trigger, and a one tooth trigger on the distributor. Using the stock sensors would require specially written code. For some mysterious reason, Chrysler designed a different trigger wheel arrangement for every different engine they made in the '90s unless the engines only differed by a bore and stroke change. The 4.0, 3.9 V6 truck engine, and 2.5/3.0 V6 all have different trigger wheel designs, and the only thing they have in common is a one tooth wheel in the distributor.

[eluis]

Hello Matt. I tried to start the engine changing the settings to 22 dase teeth and two missing teeth but the engine would not crank. What I am going to do is to use a 1987 jeep distributor with a 7 pin HEI module. I think that will solve my problem. Any suggestion I will appreciate.
Thanks.
Att Eluis.

[DonTZ125]

If the teeth are clustered 1234(gap)1234(gap)1234(gap), then perhaps an adapter circuit could be built. The VR circuit gets its signal from the crank wheel and drives a 2-bit counter (2 J-K flip-flops, and counts 0123), which then drives a one-shot as it rolls over. The one-shot output is the crank signal to the MS2 card. You now have a 3-0/1 tooth arrangement.

Will it be as accurate as a 15-1-1-1 (18-2-2-2?) decoder? Almost certainly not, but it should get the poor man on the road (or off the road, as the case may be - it IS a Jeep! ) until a developer or some other clever lad with time on his hands can write a decoder.

[Matt Cramer]

Hello Matt. I tried to start the engine changing the settings to 22 dase teeth and two missing teeth but the engine would not crank. What I am going to do is to use a 1987 jeep distributor with a 7 pin HEI module. I think that will solve my problem. Any suggestion I will appreciate.
Thanks.
Att Eluis.

Well, at least HEI is a pretty well proven option.

You might want to try an older (2.6X) code release with the current crank trigger as well - it may be that some code improvements broke some of the "code abuse" tricks.

[eluis]

Well I started the engine all ready and it runs ok, I going to try to use the original ICM module and elliminate the 7 pin HEI taking the VR signal from the distributor and sending the ignition output from pin 36 with a 5 volt pull-up circuit.
I will let you know if it works.
Thanks.
Att.Eluis.