Blowing 7.5AMP ignition fuses

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Marco7

Marco7

Joined
Oct 20, 2005
Threads
34
Messages
308
Location
TX
Hello All,

Had a no-start situation last week with my '91 TLC. Cranks strong, just won't start.

In the past, the EFI relay is usually the culprit. Replaced it with oem, still wouldn't start...no spark at coil.
Found out that the 7.5amp fuse was blown. Replaced it and it started and ran fine until the next time I went to start the truck.
This is repeated again and again.
I can tell if the truck is not going to start, because the dash warning lights will not illuminate as I turn the key.

Looked at the wiring underneath dash & behind fuse panel to see if there was any grounding out and saw nothing unusual.
I was thinking that it's the ignition switch.
I have the shop manual and there is nothing that helps troubleshoot the ignition switch.

Any help is appreciated.
Marco
 
ignition fuse

assuming that you have a petrol engined cruiser the 7.5 amp fuse also supplies power to the charge warning light, and the IC regulator in the alternator and is also connected to one of the coil terminals of the charge light relay. So the wire runs up behind the dash and also runs out through the firewall into the engine bay. The wire you are interested in should be a black wire with a blue trace (stripe) on it.
I would be looking for chafing of the wiring loom where it passes over things.
I have the same problem in my diesel cruiser where the same wire / fuse supplies all the things listed above and the fuel cut soleniod.
Get a good service manual and all the diagrams will be there. Ellery's have a very good one that I use.

Cheers
 
In later years, a short in the wiring in the fuel pump can also blow that fuse. O2 sensor wiring also blows it.

You need the EWD for your year model and start tracking down the wires if something obvious doesn't jump out at you. I think Jon has the wiring diagrams on his web site.

-B-
 
Thanks for the help guys!

Sarmajor,
I failed to mention that I did cover an exposed black/blue wire with electrical tape when I tested the coil.
It had been spliced into and is coming from the firewall.


Oddly enough, today I did not have to replace the fuse at all.

I'll check the wiring diagram again.

thanks again...will keep you updated.
 
Sorry to dredge up this thread but it seemed to be the proper one. I'm having the 7.5a blowing on my 1hdt equipped 1fzj80. Fuel pump is very loud and pumping when ignition turns on. Causes fuse to go before turning over. I don't think pump noise is relevant as its been that way since I bought her, but figured worth mentioning. Any thoughts?
 
Bisonthecruiser said:
Sorry to dredge up this thread but it seemed to be the proper one. I'm having the 7.5a blowing on my 1hdt equipped 1fzj80. Fuel pump is very loud and pumping when ignition turns on. Causes fuse to go before turning over. I don't think pump noise is relevant as its been that way since I bought her, but figured worth mentioning. Any thoughts?
Click to expand...

I'm having a similar issue with my FJ62, which this thread relates most too. Bisonthectuiser did you have any luck in resolving?

Each time when I turn the key the IGN fuse blows, but the brake light and battery light come on from the dash and the engine cranks. Just doesn't seem to want to start all the way.

I have checked most of the wiring, thinking their was a short, but have not seen evidence in that.

Thanks!
 
andrea-PE-ITALY said:
hallo from italy, same problem on my HDJ80 4.2TD. Switching on the engine I blow the fuse 7,5A....BUT.... If for first step I remove fuse, second step I turn the key and than I insert the new fuse 7,5A, the new fuse does not "burn" and the engine starts with no problems....
Click to expand...

it seem to be connected something like capacitor or something else who "sucks" current over 7,5A during switching on the engine
 
Es toyota land cruiser 1994 inyección fzj80, no es diesel, pero no sé como están las conexiones eléctricas del fusible 7.5 porque no me arroja luz, solo marca masa, no sé si lo reparé mal, muchas gracias
 
Yo creo la eléctricas del fusible 7.5A es por los Land Cruisers ante 1994 y los Land Cruisers con motor diesel.

¿Tu FZJ80 arranca?

Holy crap, iPhone autocorrect and my trash Spanish
 
I have diesel 1HD-FT. Last day the problem was back. my car has stopped on the road. by testing with ohm- meter, the output side of the 7.5A IGN is on electric ground. coil on the diesel pump has been insulated, but the ground on the wire remain. i'm very sad @the moment. Ihave no pics of location but is very simple to find, lower the place of right battery(passenger side)
 
Today I still want to tell about this damn blown IGN 7.5A fuse on toyota 80 24v and how it caused a long car stop waiting to find a fault. The 7.5 A IGN fuse is used to power pneumatic EGR valves, air resistance preheating relay, charge control on alternator, diesel solenoid valve on pump and more that I don't remember now. Only diesel solenoid valve is essential for car movement. it happened to me about a month ago that on returning home, the car stopped suddenly and did not restart. I checked fuses and found IGN 7.5 ° blown. I replaced and 10m later to start, again still burned and the car stopped. I didn't have an electric wire with me and it was dark. Called friend who towed me home. Over 40km. After a few days the car restarts as if nothing happened and while I test on road around home, the fuse still blown and the car stopped after 3km. For the past few days I have disassembled everything in the dashboard to look for short circuit that blow fuse. Nothing unusual found. I think that it is not correct that a failure of a particular non-fundamental x engine causes the vehicle to stop completely. With the help of a tester in the ohm meter position between ground and output IGN 7.5A fuse I looked for bad contact between wire and chassis but not found in the cockpit. Quite complicated to look in the engine compartment, some groups of unreachable wires. So I decided to disconnect the diesel solenoid valve from the wire that uses the 7.5 ° IGN fuse and I made a new wire only for the diesel solenoid valve, with a 3A fuse that starts from the "voltage side" of the 7.5 ° IGN fuse (BLACK WIRE- RED). In this way, if there is still ground on the original BLACK-BLUE-gray wire, if the IGN fuse blows, I can at least go home even if the alternator does not report charging voltage and the EGR system bulb and glow plugs does not work (all disassembled a few years ago ). I don't know if I can find the short circuit someday, but at least I can walk safely.

20210117_125213.webp
 
andrea-PE-ITALY said:
Today I still want to tell about this damn blown IGN 7.5A fuse on toyota 80 24v and how it caused a long car stop waiting to find a fault. The 7.5 A IGN fuse is used to power pneumatic EGR valves, air resistance preheating relay, charge control on alternator, diesel solenoid valve on pump and more that I don't remember now. Only diesel solenoid valve is essential for car movement. it happened to me about a month ago that on returning home, the car stopped suddenly and did not restart. I checked fuses and found IGN 7.5 ° blown. I replaced and 10m later to start, again still burned and the car stopped. I didn't have an electric wire with me and it was dark. Called friend who towed me home. Over 40km. After a few days the car restarts as if nothing happened and while I test on road around home, the fuse still blown and the car stopped after 3km. For the past few days I have disassembled everything in the dashboard to look for short circuit that blow fuse. Nothing unusual found. I think that it is not correct that a failure of a particular non-fundamental x engine causes the vehicle to stop completely. With the help of a tester in the ohm meter position between ground and output IGN 7.5A fuse I looked for bad contact between wire and chassis but not found in the cockpit. Quite complicated to look in the engine compartment, some groups of unreachable wires. So I decided to disconnect the diesel solenoid valve from the wire that uses the 7.5 ° IGN fuse and I made a new wire only for the diesel solenoid valve, with a 3A fuse that starts from the "voltage side" of the 7.5 ° IGN fuse (BLACK WIRE- RED). In this way, if there is still ground on the original BLACK-BLUE-gray wire, if the IGN fuse blows, I can at least go home even if the alternator does not report charging voltage and the EGR system bulb and glow plugs does not work (all disassembled a few years ago ). I don't know if I can find the short circuit someday, but at least I can walk safely.

View attachment 2578324
Click to expand...
Did you ever resolve the short? I'm having this same problem on my 1992 HDJ80 (European model left hand drive) and am over 17 hours in diagnosis time with my garage and they cannot find a wire that is shorting. I also don't have the 1990-1992 EWD, as cannot find a digital version anywhere on here or other LC sites, only the 1996 EWD, which according to my garage is different, as there were upgrades made by Toyota on post 1992 model LCs.
 
On U.S. petrol variants we have seen the A/C clutch lining completely gone causing a dead short to ground blow either the dash illumination or the ignition fuse. Some Cruisers seem to be wired so a dead short on the A/C clutch blows the dash illumination (most common and will have the IC, Charge Warning indicator and Fuel Pump blow the Ignition fuse) while others have the A/C clutch dead short blow the ignition fuse (Tthe IC, Charge Warning & Fuel Pump blow the dash illumination fuse in this variant).

I would check your A/C Clutch for a dead short. You indicated it did not blow a fuse one day you ran it. If you have the A/C off and the fuse blows when you engages the A/C I would say the A/C clutch is the culprit.
 
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