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New Distributors Installed / Tach Not Working

H

hoss1234

Member
Hello,

I just installed 2 new Mallory distributors on my 1978 318 Chyslers with electronic ignition. After installing one on my starbord engine it seemed to run great but I couldn't get the tach to work. I hooked up the distributor wire to the (-) coil terminal just as the instructions told me to do and the engine wouldn't get any spark. I disconnected the existing wire that was run to the (-) side of the coil leaving only the green wire from the distributor hooked up and it started fine but my tach wouldn't work. I called Mallory's tech support line and they told me it was a bad tach. In the mean time I replaced the port engine distributor and I had the same problem. I find it hard to beleive I had 2 bad tachs. Has anyone run into this problem when installing Mallory distrubutors before? Could it just be the tachs are not compatible because they are so old, I had a similar problem with fuel guages when I replaced my tanks. When I called Mallory a second time they said they can't help with a guage problem and they don't support any problems with the OE ignition system that is already on the boat. Does anyone have a fix for this?

Thanks
Hoss
 
What model Mallory distributor did you use? I put a Mallory YLM579AV distributor on my 360 during the rebuild and it works fine. It's the electronic distributor with everything in it that doesn't require a seperate ECU. I also replaced the original tach with an aftermarket tach that has an hour meter on it. Are you still using the Chrysler ECU? I ditched mine when I made the change.
 
I put the same distributors on but I havent replaced the tach and I'm thinking my tachs aren't compatible with these newer disributors. I had a similar problem with fuel gauges that worked fine until I had new tanks put in, the senders hooked up exactly the same but the gauges wouldn't work, put in new fuel gauge and they worked fine, it was the same gauge just newer. I do still have my existing ECU on each engine I didn't know I could get rid of them. What else runs on those ECU's? I thought it might effect other functions and instruments on the boat. Don't all of the other gauges run off of that as well?

Thanks
Hoss
 
I'm confused. (Happens all the time!) The new Mallory distributors have their own ECU built in, so why are you messing with the old Chrysler ones?

Jeff
 
I didn't know if I still needed the Chysler ECU hooked up or not. The new distributors aren't wired into them at all but I didn't know if they controlled anything else or if I should disconnect them completly. Either way I still cant get my tachs working. Jeff, Any insight you could give would be greatly appreciated.

Thanks,
Hoss
 
Is there a wire going from the Neg side of the coil to the sender term on the tach

and does the Tack "O" out when you turn the key on
 
You need 12 volt power in Start and in Run to your new distributor and to the "+" coil terminal. Eliminate the old ECUs and everything going to/ from them. That might be causing your mystery tach problem.

Jeff
 
Thanks Jeff I'll try that!

Grease Monkey,

There is a negative coil wire but when I leave it hooked up I get no spark. When I disconnect it and just connect the green wire from the distributor as the instructions tell me to do I get spark. I disconnected the wire both at the coil and up at the tach and used a jump wire thinking that it may be a short in that wire but it caused the engine to stall. For some reason when the existing negative coil wire is hooked up it shorts out. This happens on both port and starbord sides.

Hoss
 
Jeff,

It is still going to the old ECUs but disconnected it at the coil and at the tach and then ran a wire directly from the negative coil terminal to the back of the tach bypassing the ECU and it still caused the engine to stall.

Any thoughts?

Hoss
 
Thanks Joe,

After you unpluged the ECU did you have to bypass the existing tach wiring or did the tach work for you? I would imagine you had to bypass it since it's wired through the ECU but just checking.

Thanks
Hoss
 
Hoss
once you unplug the ECU, the original neg coil term wire goes only to the tach.
you wind up with two wires on the coil neg term/ the green one from the mallory ign module and the original black/grey tracer for the tach.
Joe
 
i am about to do the same dist replacement and i was at first worried about eliminating the ecu. my ballast resistor is a 4 terminal unit. can i reuse it or do i need to repl it with a 2 terminal? its my impression that the purple wire off the ballast resistor is the tach, is that correct? i purchased ylm549av mallory distriutors and was confused when i got to the boat and it was 3 wire and i have 2 wire dist. the guy at summit racing said i could rewire the distributor to make it a 2 wire but that could get ugly he said , he suggested eliminating the ecu. has anyone else done this and it works fine?
 
No need for the Chrysler ECU with that distributor. I have it as a stand alone unit and it works fine. It also works with an MSD box if you want to add one. I use a two terminal resistor.
 
I reconnected the black wire to my coil which sends the signal to my tach then I disconnected my Chysler ECU and the tachs worked fine and the boat ran great. It had more power and I was able to get on a plane with the engines struggling. Now that my tachs are working I do still have a problem with my starbord engine. Prior to the new distributors I couldn't get over 2200 RPM at WOT now I cant over 2800 RPM. I do have a lot more power and boat is going faster, I'm able to get around 20 MPH but before I had this problem 20 MPH wasn't even half throttle for this boat. The top speed of this boat before I installed the new distributors was around 12 MPH on a good day. I think a compression test might be my next step. Anyone have any thoughts.

Thanks,
Hoss
 
1. Check to make sure all the wires are on the right plugs (which could not be the case after all the thrashing you've done).

2. I assume you retimed both motors?

3. Are the carbs getting enough gas? If the motor makes power initially, then sags badly, you have a fuel pressure problem. (I'm going through this with one of mine at the moment.)

4. Run it hard, shut it right down, then pull plugs and read the colors. Stark white indicates fuel starvation of incorrect timing; dark brown says ignition problems (wires, plugs, etc).

Jeff

PS: Don't give up! You're close to total success.
 
i have gone through this lack of topend power thing and after reading all the posts i can find on the subject i have tried : replaced all filters, rebuilt the fuel pump, had carburetor rebuilt, then after exercising the advance springs (rusty in there) i could not find the parts for the distrutor (prestolite) so i purchased a mallory ylm549av and installed it it seems more responsive when gassing it in neutral but can not get over 2900 rpms on the water. still have the same problem. this engine does use some oil so i assume its a little tired but this thing ran fine last season. also had the props ck'd and they are now up to original specs. what the heck is next ? starts and idles easily. please help.....
 
Run it hard, then shut that motor off fast as you can--do NOT let it idle. Let her cool down, then pull the plugs and read the colors. Be sure to record the cylinder # and color for that cylinder.

Jeff
 
Thanks Jeff,

I'll try that this coming week end. I've been chasing this problem for quite a while and prior to installing a new distributor I did replace all filters as I do at the start of every season & Last season I replaced the fuel pump and the carb. Checked under a load to make sure the secondaries are opening and they are. I'll look at the plugs this weekend. It's my understanding a stuck valve can cause this as well. I'm in the automotive bussiness but I repair wrecks so anything past the basics of an engine I'm a little lost. Does anyone know if that could cause a problem like this or would I see other signs if that were the case?

Thanks
Hoss
 
STOP!!!!!!!!! The first thing to do is check the total timing at 3000 rpm. Many people time the reverse engine wrong. You should have 28-30 degrees at least.

Dan
 
Thanks Dan,

After installing the new disributors thats the first thing I checked. Both engines are advancing 28-30 degrees at around 2500-2800 RPM.

Hoss
 
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