Fuel Starvation and Capacitive Discharge // 97 LX450

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bonestock

Transportation Specialist
SILVER Star
Joined
Feb 26, 2015
Messages
2,179
Location
Lookout Mountain, GA
Went on a multi-day trail ride over mostly Forest Service roads and, on the 3 day, I began to lose power to the point that I was no longer able to move under my own power. It seems as if I was running out of fuel. Sitting level with 1/4 tank of fuel, it would idle fine but, when put into gear, it would die as soon as you touched the skinny pedal. Fooled around with it for a minute to no avail. My buddy, @Jboyd, did what he called a capacitive discharge where he touched the negative battery cable (all of them on the terminal) to the positive post on the battery...

Truck started up, ran fine for about 3 days of limited driving. Got me home and around town for a total of maybe 100 miles. Started acting up again and opted to replace the fuel pump to no avail. Replaced the EFI relay in the under-hood fuse box and the fuel pump relay mounted to the inner fender. All to no avail.

Had it towed to the shop where another capacitive discharge seems to have done the trick. Thought I'd throw this out there...
 
Went on a multi-day trail ride over mostly Forest Service roads and, on the 3 day, I began to lose power to the point that I was no longer able to move under my own power. It seems as if I was running out of fuel. Sitting level with 1/4 tank of fuel, it would idle fine but, when put into gear, it would die as soon as you touched the skinny pedal. Fooled around with it for a minute to no avail. My buddy, @Jboyd, did what he called a capacitive discharge where he touched the negative battery cable (all of them on the terminal) to the positive post on the battery...

Truck started up, ran fine for about 3 days of limited driving. Got me home and around town for a total of maybe 100 miles. Started acting up again and opted to replace the fuel pump to no avail. Replaced the EFI relay in the under-hood fuse box and the fuel pump relay mounted to the inner fender. All to no avail.

Had it towed to the shop where another capacitive discharge seems to have done the trick. Thought I'd throw this out there...
I've never heard of a "capacitive discharge" on a vehicle other than a condenser on the old cars with breaker points for the ignition. You had to work hard at getting bit by those.

If that indeed caused a difference in how the truck ran, then you need to check the ground cables on the engine and to the body.

Also, replace your gas cap, charcoal canister, fuel filter, and pump filter sock inside the gas tank. I'm guessing you were at elevation when this occurred. The bigger possibility is that the E-15 fuel that you had in the tank started to boil and caused other issues with properly getting fuel to the engine. Having a bad gas cap, charcoal canister and check valve could cause an issue with the tank either pressurizing or creating a vacuum and not delivering enough fuel.

I think it was coincidence that stopping and touching the battery gave the truck time to vent or you filled with fuel and it allowed the change.
 
I've never heard of a "capacitive discharge" on a vehicle other than a condenser on the old cars with breaker points for the ignition. You had to work hard at getting bit by those.

If that indeed caused a difference in how the truck ran, then you need to check the ground cables on the engine and to the body.

Also, replace your gas cap, charcoal canister, fuel filter, and pump filter sock inside the gas tank. I'm guessing you were at elevation when this occurred. The bigger possibility is that the E-15 fuel that you had in the tank started to boil and caused other issues with properly getting fuel to the engine. Having a bad gas cap, charcoal canister and check valve could cause an issue with the tank either pressurizing or creating a vacuum and not delivering enough fuel.

I think it was coincidence that stopping and touching the battery gave the truck time to vent or you filled with fuel and it allowed the change.
Gas cap is new OEM less than 6 months old.
VC120 canister swap/mod is 3 months old.
Fuel filter is about 15 months old.


I used to hear a “whooshing” sound from the gas cap that was only resolved by a charcoal canister.

All body grounds have been upgraded and recently checked when I had the transmission out for a rear main seal.

This thing gets a ton of work regularly and is only a lift at least 1x/ month. Really really hoping that the new fuel pump does the trick once the ECU relearns with the new bits.

I was just reporting something that worked to get me off the trail when options were limited. I’ll
Report back here as updates become available.
 
Gas cap is new OEM less than 6 months old.
VC120 canister swap/mod is 3 months old.
Fuel filter is about 15 months old.


I used to hear a “whooshing” sound from the gas cap that was only resolved by a charcoal canister.

All body grounds have been upgraded and recently checked when I had the transmission out for a rear main seal.

This thing gets a ton of work regularly and is only a lift at least 1x/ month. Really really hoping that the new fuel pump does the trick once the ECU relearns with the new bits.

I was just reporting something that worked to get me off the trail when options were limited. I’ll
Report back here as updates become available.
You've obviously put a lot of work into this. I am curious what you find.

Possibly check your temp sensor and wiring, as when the temp comes up, the O2 sensors are verified and the ECU switches from open to closed and the fuel pump speed changes. It's possible there's something related to that.

If anything else comes to mind, I will post.
 
The process apparently discharges all capacitors in the system.....and can "fix" some strange electrical gremlins. Since this worked for this problem I would suspect more advanced electronics like ECUs than sensors, relays or pumps.... but OTOH maybe a faulty part could send the wrong info to an ECU and this procedure resets the ECU? Let us know what you find!

edit: At first I thought the battery was being shorted to ground... I now see that its not and removed my warning but be careful if you have two batteries.
 
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Just an update here on my loss of power / fuel starvation issue.

The wire from the coil to the dist. cap (90919-13436) had some how become somewhat dislodged at the dist. cap. Corrosion and general $hittiness had occurred inside. Replaced the wire, cap and rotor and everything seems right in the world. I am now throwing a 301 (cylinder #1 misfire) code that I have seen sporadically in the past but not for a while. Maybe the ECU? Maybe an injector?

Getting a partsouq.com order going now and would like to also replace the spark plug tubes while I am doing the valve cover gasket, injectors, injector bits, intake manifold gaskets, throttle body gasket and spark plugs. The wires are pretty new and seem fine some and I will try to avoid that cost unless it turns out to be needed.

The next bit is cross posted here.

Anyone have a part number for the spark plug tube itself? I, too, searched using a popular search engine and was only able to find the gaskets that go on the topside of the tubes at the valve cover. There are some pretty sophisticated parts guru's on here that will hopefully stumble across this request.

I've got to be getting close to having replaced every damn part on my truck at this point... Right, right?
 
Just an update here on my loss of power / fuel starvation issue.

The wire from the coil to the dist. cap (90919-13436) had some how become somewhat dislodged at the dist. cap. Corrosion and general $hittiness had occurred inside. Replaced the wire, cap and rotor and everything seems right in the world. I am now throwing a 301 (cylinder #1 misfire) code that I have seen sporadically in the past but not for a while. Maybe the ECU? Maybe an injector?

Getting a partsouq.com order going now and would like to also replace the spark plug tubes while I am doing the valve cover gasket, injectors, injector bits, intake manifold gaskets, throttle body gasket and spark plugs. The wires are pretty new and seem fine some and I will try to avoid that cost unless it turns out to be needed.

The next bit is cross posted here.

Anyone have a part number for the spark plug tube itself? I, too, searched using a popular search engine and was only able to find the gaskets that go on the topside of the tubes at the valve cover. There are some pretty sophisticated parts guru's on here that will hopefully stumble across this request.

I've got to be getting close to having replaced every damn part on my truck at this point... Right, right?
The actual tubes are pressed into the head and are not typically replaced. The Spark Plug Tube Seal is the top of the tube to the valve cover.
 
Corrosion and general $hittiness had occurred inside. Replaced the wire, cap and rotor and everything seems right in the world. I am now throwing a 301 (cylinder #1 misfire)
You didn't mention replacing the spark plug wires. If the lead wire was corroded, I'd expect the rest of them to be, too.

The NGK set from RockAuto works great.
 
You didn't mention replacing the spark plug wires. If the lead wire was corroded, I'd expect the rest of them to be, too.

The NGK set from RockAuto works great.
The Toyota cap, rotor and wires work great too!
 
Normally I would buy wires on the quick but I’ve got to stop the money bleed somewhere. This may end up turning into my build / maintenance thread.

I just replaced the brake booster and master cylinder and a significant portion of my exhaust.

I need to just get some love back for a minute.

Edit: ordered the Denso set from Rock auto. Good call.
 
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UPDATE-

Logged abut 50 miles with no issues so far. Fingers crossed. Still looking for a parts number on the spark plug tubes.
 
Any ideas why the cap discharge process helped overcome a corroded connection? At first, when I thought the process involved drawing a large amount of current to ground I was buying that it could blast through some corrosion but now that I see its just equalizing positive and negative I'm curious....any ideas out there?
 
As stated previously the spark plug tubes are NOT replaceable. The seals are.

I'm never a proponent of firing the parts cannon at a rig unless you are baselining it. True diagnosis takes time to understand how to do and time to actually perform, but the payoff is not spending money on parts you didn't need.

If the issue persists you will need to start diagnosing with an oscilloscope. I'll keep my eye on this thread and can help you with that level of diagnostic work if you get to it.

If you don't have your FSM downloaded already stop what you are doing and download it right now, like right this second. They are in the resources tab here or you can just click the link in my signature. There are complete flow charts in the FSM to help diagnose issues just like this.
 
At first, when I thought the process involved drawing a large amount of current to ground I was buying that it could blast through some corrosion but now that I see its just equalizing positive and negative I'm
Yeah, it was just resetting the ECU, causing it to behave more conservatively while re-learning. It wasn't doing anything to solve the actual problem.
 
parts cannon
I'm going to start using this expression. At 200K miles, if a part hasn't been replaced I'm going to confetti my love with OEM glory. I, too, am not a fan of throwing parts at something but I am ordering them all the same because, as with all things, nothing lasts forever.
As stated previously the spark plug tubes are NOT replaceable. The seals are.
You are correct, they are not replicable. Seals have been ordered.
If you don't have your FSM downloaded already stop what you are doing and download it right now, like right this second. They are in the resources tab here or you can just click the link in my signature. There are complete flow charts in the FSM to help diagnose issues just like this.
I've got hard copies. I just hate using them for the diagnosing procedures.

I appreciate the frank feedback!

Yeah, it was just resetting the ECU, causing it to behave more conservatively while re-learning. It wasn't doing anything to solve the actual problem.
Agreed! The ECU has been suspect for a while now and I've ordered one (used in good condition) to keep as a trail spare for the inevitable.
 
Just spitballing here, but doesn't removing the EFI Main in the engine bay fuse block reset the ECU? This seems like a much safer way to isolate a problem.

Also, I too can't find the spark plug tubes, but the FSM has a procedure for replacing them.
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Maybe @OGBeno can shed some light on why they don't seem to be listed separately, even though the head doesn't (didn't) seem to ship with them.
 
Just spitballing here, but doesn't removing the EFI Main in the engine bay fuse block reset the ECU?
Yes. The ECU can be reset by pulling the 15 amp EFI MAIN fuse OR by removing either battery terminal OR by unplugging and removing the ECU itself. They all accomplish the exact same thing.
 

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