ive had a long history with electrical issues on my 1971 fj40. The latest is weak or no spark while cranking the engine over... it wants to start after I let off the starter. I’m not electrically inclined... but I know there is some mechanism to increase power to the starter when starting. This is robbing juice from the ignition system. Help! FYI... I have a four wheeler that has the same issue... it only wants to start as I let off the starter button. What gives???
Weak spark while starter is engaged (1 Viewer)
- Thread starter raymond2335
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
My first test would be to put a volt meter or a test lamp on the coil input. You should have 12 volts there when key is in the run position as well as in the start/cranking position. This would tell if your ignition switch is working properly. If it is then I’d check the ballast resistor bypass circuit (if yours has it) which gives more voltage to the coil when cranking.
But I’d start with the ignition switch. It’s a common cause for the symptom you describe.
Let us know if you need help with the first test.
But I’d start with the ignition switch. It’s a common cause for the symptom you describe.
Let us know if you need help with the first test.
Last edited:
Looking over the wiring diagram here, it seems as though you just have the ignition switch going to the starter and coil/distributor. Fuse panel, wires and grounds seem to be all that are involved. Have you checked your points recently? Maybe the rub block is worn or they need adjusting, not opening enough.
I had a heck of a time over the summer chasing down electric issues that were causing a non-start. Be sure to check all of your grounds for cleanliness and good contact, and the same in the fuse box.
This is a key point and if it reacts like that always then I would suspect the ignition switch.
Recently, I purchased a 1973 Toyota FJ40 with the intent to rebuild it with my 14 old Son as a project car. We have a spark problem that has gotten both of us scratching our heads. I have replaced the starter solenoid, ballast resistor, rotor button, and rotor cap. Also, we replaced the coil, condenser, and threw a new set of points in it ("properly gapped"). I have checked all fuses, checked for voltage and continuity with a multimeter, reset the timing. The car runs, "sometimes" but seems to have a mind of its own. AT one time we had it running; rough I might add. We made adjustments to timing and carbourator and it seemed to get slightly better but nowhere near to perfect. At one point we found that #1, #3, and #6 were not firing; now nothing is firing. It's slightly frustrating. Also, I was thinking about worn lobes on the distributor, which would affect spark -right? I was wondering if you had any ideas that perhaps you think I ought to try?
- Thread starter
- #7
New ignition swith
...
I had a similar issue for a time... ran only on three cylinders...no spark on the others. turns out I had switched a couple of plug wires accidentally.
- Thread starter
- #8
Does anyone know of a shop or Machanic in the Midwest (Iowa) who knows Landcruisers?
I had the same issue with my suzuki sierra. It would only want to start when letting the key off. Turned out it was the coil failing it did not have enough grunt to run the car with the lower voltage while cranking.
A way to test this (and also a cheap temporary fix) is to run a wire from the starter solenoid up to the coil bypassing the resistor so you have full voltage on the coil while cranking, then when you let the key off it returns to running normally with the resistor in play
A way to test this (and also a cheap temporary fix) is to run a wire from the starter solenoid up to the coil bypassing the resistor so you have full voltage on the coil while cranking, then when you let the key off it returns to running normally with the resistor in play
X2, Measure the voltage at the coil while cranking, even if you do have a new switch (especially if you still have the original 50 year old harness). It's a quick easy test to see how much voltage drop you are seeing at the coil.
This is probably why Toyota added a wire from the starter solenoid directly to the coil (bypassing the ballast resistor) to supply full battery voltage while cranking. You can see this on the schematic that Byron posted, starting with 1974.
Great! Thanks for the advice. I will go and check it out. I will let you know what I figure out.
The electricity is bleeding of through many other connections in the harness and dropping voltage from the starter load.
I have HEI on my Chevy engine so to be sure I am getting enough juice to the coil I put in a relay that clicks on with the starter and supplies voltage straight from the battery.
I get 13-14 volts to the coil this way. That is with head lights and heater going.
You may need a ballast resistor depending on what ignition system but the relay would still get you full voltage to where you want it.
Before you go through all that make sure you have a good battery and charging system.
I have HEI on my Chevy engine so to be sure I am getting enough juice to the coil I put in a relay that clicks on with the starter and supplies voltage straight from the battery.
I get 13-14 volts to the coil this way. That is with head lights and heater going.
You may need a ballast resistor depending on what ignition system but the relay would still get you full voltage to where you want it.
Before you go through all that make sure you have a good battery and charging system.
