I have had this problem once before and my mechanic fixed it.
ok -- driving normaly and the engine just cuts out. try to restart and it wont lite at all and the tach is resting on 0 the whole time.
when my mechanic fixed it the first time he said it was the ignition module (mine is the '86 and up with 8 connectors.
but of course he also replaced cap and rotor.(free - hes anice guy)
when I was helping him we found that the engine would run with the white tach wire ( the one coming off the external coil) disconnected.
anyway the car has run fine with only those 3 changes until now when this happend again.

so I ordered the replacement module from accel and looked at the cap+roter which were fine. BUT now the car will not run with the new module unless I again disconnect the tach.

when I tried to start it with everything connected the tach wire got searing hot and I assume this circuit has grounded. I thought the ground was through the module like last time (or was it?) but this time that seems untrue.

Help me if you have simmilar experience.
It still runs just with no tach. my info is in sig.

------------------
88 T/A 305 TPI--
K&N,Air foil,hypertech chip, thermostat+fanswitch
no MAF screens, no cat, dynomax exh, urethane motor+trans mounts,
SSM frame con, Bilsteins
homemade ramair.

 

Your intial diagnosis is correct. That is, your tach wire is grounded somewhere. This is probably a different problem than your module one, but it produces a similar result.

I would start at the tach noise filter, which is a small silver can mounted on the firewall right behind the distributor.If you follow both of its wires, you will see that one plugs into the dist and one goes toward the bulkhead cannector and then on to the dash. Try plugging the tan wire into the distributor and see if that fixes it. If so, then the filter is bad. If not, the problem is wiring, the flexible circuit behind the dash, or the tach itself.

------------------
"So many Mustangs, so little time..."

 

Ok I bet you wont know what to say now!

I found this silver filter but im not sure If thats what it was. it had a flat type ground connector with a tan wire but this just lead into the harness to the dash. I unplugged this. then I found the other tan wire that has a connection by the ac accumulator. I unpluged and cleaned this. then I plugged my white tach lead from the coil back in and started.

It started right up and the white tach lead was cool. so I decided to plug the tan ground back into this silver thing and the engine just kept on running.
this ****ing thing is now running with all the old wires just where they were when I first could not get it started 30 min. ago

what the hell is going on and did I find the rc filter if there was no wire to the tach??
Im not sure that I have such a thing?? do I? there dont seem to be any connection to my distributor except through the module weather packs. do you mean that somewhere down the line the filter plugs into the harness before it gets to the distributor??
just for clarification it is an 88 LB9 305 with external coil.

thanx
and good luck figuring this one out

[This message has been edited by 88305tpiT/A (edited November 27, 2000).]

 

Yes that was the filter. The tan wire by the accumulator has nothing to do with it. The filter is sort of "in line" with the tach wire; the white wire plugs into the coil connector, the signal from the coil goes through the filter and gets filtered, and the tan wire goes into the bulkhead connector like all the rest of the wires that are going to the instrument cluster and elsewhere inside the car and takes the RF-less signal to the tach.

Sounds to me like the wire may be chafed somewhere, or just the act of disturbing the filter may have made it unshort. I would bet money that it will do it again someday when you are least able to deal with it, I'll let you imagine the worst possible scenario and it probably won't come close. But seriously, you obviously disturbed the gremlin, so you know where he lives; look closely and you will find him.

------------------
"So many Mustangs, so little time..."

 

thanx a million times for the help.
I will look into replacing as much of the tach string as I can.

this message board is a godsent for stuff like this and I know we all love our third gens but

GOD DO THEY HAVE GREMLINS!!!

just my 2cents
James

 

Gremlins like this are in every car! My brother-in-law just had to take his 2000 Ford Exploder, er...Explorer...in for work that turned out to be a ground wire loose, or corroded, or something like that.

The gremlin I want to track down now, is the one that makes the voltmeter vary with the turn signals flashing. I know where to look, I've tried the remedies, but it still happens! I guess I can just live with it, but..... :-)

------------------
Working on:
'84 Z28 LG4 305
Added dual elec fans.
145 MPH IROC Speedo
Building 430 HP 350
using primarily GMPP parts.
Block is in shop!

Awaiting results from all 8 ASE tests.

Starting to look like the Kicker poster child!

 

you think you have gremlins
ohmygod you dont know.

I have gone through 7 alternators in the 3 years I have owned the car and there are so many possibilities that it makes my head spin just thinking about trying to track it down.
my vmeter does the same thing and the left side of my tach sometimes goes dark (could be related to the problem discussed here), dont even talk about the cruise control and if i had a quarter for every time i found something that the previous owner juryriged....

 

ok
you were right it just did it again this morning in the middle of a 4 lane intersection.

same thing -- got out and unpluged white tach wire which was burning hot.
drove it home and unpluged the tan filter connect while still running then pluged white back in , then pluged tan back in.

I am starting to think that my car just doesnt want to live anymore because it was a simmilar feeling to having it stop on the tracks with an oncoming train.
I had to hustle to push it out of harms way!!!

any way I think today I will replace that rf filter before it cuts out on some real tracks!!

God **MN F***ING GREMLINS.

hey wait a minute I just realised something.
the tach worked when I had the filter tan wire unplugged.
I thought you said that this connection was inline to the tach. how could the tach work then???
I figured part of it out.
the wire I had (tan) wasnt the filter, it was the oil press lead.
I never really did find any other parts that looked like what you are talking about


[This message has been edited by 88305tpiT/A (edited November 28, 2000).]

[This message has been edited by 88305tpiT/A (edited November 28, 2000).]

 

could a moderator please duplicate this topic in the electronics section.
thanx

 

Unplug your Tach :0



------------------
85 Z28 - Daily Driver
60 Ranchero - Project ( Money Hole )

 

I've got a saying for electrical problems that seems appropriate in your situation. "When you open the door, the toilet flushes!" Not trying to be rude, just thought you might get a kick out of that little saying! What really sent chills up my spine is when you mentioned the last owner jury rigging things! I ended up changing out the entire dash harness in my 69 Camaro a long time ago because the previous owner thought he was the brainchild of Thomas Edison! Too funny.



------------------
89RS w/350 TPI; 69RS/SS w/450 HP 350/Muncie 4-Speed "Too weird to live, too rare to die."

 

this saying is right on the money pat.
it used to be when I pull the hood release the hood wouldent pop up until you slammed the door!!
but seriously I have been giving the harnesses a thorough going over and now I plan to go to the boneyard just to see what a real tpi setup looks like.
I have a crimp connector connecting the tan and black wires to a ground on my valve cover when these should be going to a tach filter.
there are countless things like this on the motor and I am just getting started cleaning them up.
if anyone would like to share their electrical horror stories I would love to hear them

James