Electrical issues

Picked up a new project truck today. It’s got some electrical issues as a result of the previous owner jump starting a humvee (24volt). He tried replacing the ECU spark plugs and a bunch of fuses.


The symptoms are a very rough idle that eventually stalls out and multiple misfire codes.


I have verified the fuses are good and cleaned the Maf. It’s got 325k on it and 130k on the timing belt so my thoughts are to baseline it with new timing belt-water pump and coils. But it would be good to have some direction before I start throwing parts at it. Anyone dealt with this before?

 

Welcome. I don't mean to be gruff, but I'd say you're starting at the right place. Get those things done and report back if you end up having any lingering problems.

 

Is the battery good? It should be tested. How about the alternator? It needs to be tested as well. Introducing over-voltage is going to mess with those two components first. I would imagine if the ECU isn't seeing steady voltage it's not going to be happy. And yes, the timing belt is overdue.

 

I see rustiness thru the bumper hole. First thing to check is the frame, before you invest time.

Have no idea what I'm talking about? Start here: https://www.tundras.com/threads/so-you-wanna-buy-just-bought-a-1st-gen-tundra-eh.115928/

You'll find the factory service manual and links to wiring diagrams on the 4th line, but I recommend reading the first two replies of that thread before you invest any time.

 

Battery reads just above 12 volts when it initially starts up voltage goes up to 14volts then drops down to 12.8 as the engine starts to run rougher and slows down and dies total time about 30 seconds.

The frame definitely has some flaking rust but no holes I did go over it extensively before I purchased it. I bought it to be my winter beater to keep my FJ60 out of the salt. Figure I’ll fluid film it and get a few years out of it. It was serviced regularly at Toyota through 250k

There are a couple 1st gens in the local wrecking yard that I could potentially get sensors and such for cheep

Also the LBJs have the plastic shield on them which I thought was a 06 thing?

 

Be sure and get the Aisin water pump and timing belt from a reputable source like Rockauto and not scamazon so you get genuine parts. That and the ignition coils (denso only) and sparkplugs too. While your in there it would be a good idea to go ahead and do the radiator to avoid the possibility of pink milkshake.

The boot started in 02 but it's a slightly different style than the 04-06. If those haven't been done recently you should probably consider doing those as well.

 

First things first, get the battery tested, STAT. It's the heart of the electrical system and you need to make sure it's OK. Not just because you're seeng roughly half a cell's worth of voltage drop AND the battery is operating below where I'd want to see it, but based on what it just had happen to it.

If it's OK, I've pull the alternator and have it tested next, but note: You really should only use Denso brand alternators in these trucks unless you want to be replacing the alternator every 3-5 years and/or dealing with potential gremlins from here on out. Aftermarket starters, alternators, and fuel pumps have become absolute trash over the last decade or so. Don't let the parts store sell you on it. You can look up the alternator you need at www.densoautoparts.com and if it's not in stock somewhere, I can fetch the OEM part number if you want. You can install up to 100A alternator in 2002, I believe. You can also update the alternator to a newer 130A if you re-pin the alternator plug.

Let us know how you fare on those two. But yeah. Battery first so your power station is known-good. Then alternator so you know charging of the battery is good. Any chain auto parts store will test both for free. Gates' green "HD" belt is a great replacement, may as well update that too while you're in there, since you've gotta remove it to pull the alternator. FYI, you need to remove one shared bolt with the PS pump, then loosen another bolt shared with the PS pump to pull the alternator.

 

Alright I’ll get the battery/alternator tested. I hear you on the quality/OEM parts.

This may all be mute as I did a compression test last night (should have done that before purchase) and the whole passenger side was low at 60 driver side was consistently 180. I poured some oil in one of the low cylinders and it came up to 90 I’ll do a leak down test tonight to try to narrow it down a bit more I could handle a head gasket but if the valves are messed up I’ll probably pass it on. Also I pulled the timing cover enough to verify the belt looked ok just thinking maybe the passenger side cam gear skipped a tooth and bent the valves.


On the radiator is there an oil cooler that is the concern? I know the trans cooler is separate. Is there a recommended make on that?

I went through the broken LBJ thing on a DC I used to have definitely want to avoid that.

 

There is also a transmission warmer/cooler in the main radiator.

 

If that was a head gasket, I would expect to see 1 cylinder, 2 cylinders, but not every cylinder at the exact same pressure. Before you dig into that fucker, did you check the timing? Just to make sure valves on bank 2 aren't opening at the wrong time, and that's the source of both the shitty idle. Don't expect the seller to tell you the truth on this one! I suspect the '24v jump' is potentially bullshit. Some people just can't help but strum up stories rather than admit they did something stupid, like get the timing wrong while doing the timing belt on their own.

To that point, have you checked the condition of the timing belt to at least confirm it's ever been changed? Snapping a belt can brick the engine, it's an interference engine (low interference, but we've seen boat anchors happen in the past). I'd love to see a pic. Simple to look at it, 10mm socket, loosen a timing cover enough to lift and expose the belt.

 

I think you may be right on the botched timing belt install.

 

Ended up going ahead and changing the timing belt/water pump with an Aisin set. My thought was if the valves were bent it would not have even had the 60 psi compression. Turns out I got lucky as it has full compression and runs great now. Thanks for you guys help!

 

Yeah, that compression test was really the red flag for me you were out of time. PO botched that one, or something jumped. Either way, congrats, and glad you got it solved! And it sounds like you may’ve gotten a great deal for a truck that just needed a tiny bit of tedious work.