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'95 Minicab Van engine issues - loss of power, fouling, overheating

Discussion in 'Mitsubishi Minicab' started by Jacob Field, Jan 5, 2023.

  1. Jacob Field

    Jacob Field New Member

    Hey all, having some engine issues with my '95 Minicab Van and looking for advice.

    Owned it about a month now. Replaced the water pump shortly after I got it, it had been running just fine, kept running fine after the new pump. (It sounds like there might be a special bleed procedure I should have done/should do? Are the instructions here accurate? https://minitrucktalk.com/threads/1989-mits-rhd-overheating.7312/#post-52320) The only issue I'd been having was hard starts, I usually had to crank it longer and pump the gas to get it to start.

    I was driving it going around 55/60, and it suddenly (like a switch being thrown) lost power and started slowing down. The engine didn't stop, it just suddenly lost a significant amount of torque. I'd been keeping an eye on the temperature gauge and noticed shortly afterward that it was higher than normal (about middle of the range, versus hovering around the low mark like it normally does). I pulled over and checked everything out. Engine was idling well enough but I could hear hiccups/hesitations pretty frequently so I assumed it was missing. The engine cooled down pretty quickly and I needed to get home so I took it back out. Same issue started happening about 10 minutes later with heat rising, so I slowed down and it kept cool enough to get home.

    I don't think this is a cooling system issue, since I've been driving it at 55/60 a LOT over the last month and hadn't had a speck of overheating issues before that -- my guess is that it was overheating because the engine suddenly had a lot more load (I assume one cylinder wasn't doing any work) -- but I'll take suggestions.


    I've been troubleshooting it for the past week. So far I have done the following:
    • Checked oil/coolant for each other, both seem clean.
    • Replaced the fuel filter
    • Put Seafoam in the tank to help clean gunk that could be causing issues
    • Did a compression check with a cheapo harbor freight tester. All cylinders read about 120PSI, which is lower than the 180ish it sounds like it's supposed to be (though I got ~180 with another fitting on the same tester, so I'm not sure if it's just leaky -- at least the reading is consistent so I know it's not one cylinder)
    • Replaced spark plugs: Two were fine, one was VERY fouled/wet (black crud with white deposits)
    Checked distributor cap/rotor. They seemed pretty corroded so I cleaned/reinstalled them and have replacements on the way. After I replaced the plugs, it ran MUCH better. I took it out and drove it around for ~30 minutes at speed and it was running almost as well as before (or as well, it's hard to tell). Was happy about that and parked it.

    Bought a new air filter, swapped it in, and decided to see how it ran. It's started up great since the new plugs. It started fine, and I got it partway up my driveway before it started bogging down like crazy (in first gear) when I tried giving it more gas to switch to 2nd. When doing this, it pours out a LOT of white/grey smoke. Less so when idling, and during idle it doesn't sound like it's missing, but I could be wrong. The only thing that changed since the new plugs was I accidentally broke off what remained of the plastic nipple for a vacuum hose (going from the air intake shroud to who knows where) when I was replacing the air filter. I 3D printed a replacement and epoxied it in place and no change, so it wasn't that.

    Here's what I'm thinking of doing next:
    • Check the new plug in the cylinder that had the fouled plug and see if the new one is fouled
    • Check the fuel pump relay (Anyone know where this is?)
    • Check if a full 12V is getting to the fuel pump connector
    • Get a fuel pressure gauge and measure the fuel pump output (The manual I have says ~40PSI at idle, ~50PSI at 2000RPM)
    • Follow the instructions I found on this forum thread to check the vacuum advance on the distributor (https://minitrucktalk.com/threads/p...MkBNA2q_Hh6x8Vsi-fmjuSl9gruF-RADcQ#post-94057)
    • Learn about the wet choke system, maybe try flushing/refilling coolant and doing the bleed procedure once I find info on that.
    Any help, leads, or advice would be greatly appreciated! I love this van and have been excitedly doing a mini weekend camper conversion on it, but it won't be good for much besides backyard camping till I get the engine working ;)

    (Oh, attached are photos of the plugs, and the host I accidentally temporarily disconnected)
    plugs.jpg tube.jpg
     
  2. Bowe

    Bowe Member

    Would be nice to pressurize cooling system and stick a boroscope in cylinder #1, although if it is leaking coolant into cylinde the engine may need warmed up for it to occur.
     
  3. 5Speed

    5Speed Member

    Sorry to hear, I had a similar issue with a 99 Saab. The white smoke was coolant from a blown head gasket. I had noticed some white smoke when starting the car in the morning, but it ran fine, and the smoke would soon disappear. Apparently, the gasket had a very small leak. One day as I was driving, I needed to accelerate harder than usual, and the car stumbled and blew a large cloud of white smoke. As I limped home the temperature started to rise. Long story short; blown head gasket. Check for coolant in the oil.
     
  4. Jacob Field

    Jacob Field New Member

    Thanks for the replies, all. I suspect it's a head gasket and coolant is fouling the first cylinder. Probably a small leak since I haven't noticed any coolant in the oil or vise versa, yet. But will have to check again.

    At least this is a tiny engine, I'm sure it'll be easy to work on when I get it out from under the van!
     
  5. Jacob Field

    Jacob Field New Member

    After some more troubleshooting, here's the symptoms I've found and the diagnosis I've settled on:

    Plug #1 keeps fouling. It smells like fuel and has oil on it. The oil is likely due to either worn rings or worn valve guides letting oil into cylinder. My bet is on the valve guides.

    Coolant is foaming. This could have caused the overheating I experienced. I used an exhaust gas tester to check for a head gasket exhaust leak into the cooling system. That's not what's happening. However, I've seen a couple of mentions of there being a bleed procedure for the cooling systems here and that you need to do it when draining/replacing the coolant. I did not do this when I replaced the water pump, so I suspect there's an air bubble or pocket causing foaming.

    My plan to diagnose further is:
    • Redo the compression test with a better tester. Do it as normal, record values. Do it again, after squirting some oil into the cylinders. If the pressure increases, the oil was probably sealing worn rings and I know my issue is probably the rings (or so I have read elsewhere). If that doesn't change anything, then it's more likely my valve seals.
    • Perform the bleed procedure on the coolant system. I should probably drain, flush, refill, and bleed just to be safe. Also, I'm gonna check if I even have a thermostat - the engine seems to take longer than I would expect to heat up, and when I ran it with the radiator cap off, I could see coolant churning while the radiator was still barely warm to the touch.
    I've read you can redo the valve seals without dropping the engine and removing the head. Is it really worth it? I feel like trying to work in cramped confines might not be worth the extra amount of work to drop the engine. But maybe my lack of experience is making me naive :)

    Just in case the plug fouling is related to spark, I plan to replace the plug wires. I already tested the coil resistance and replaced the cap and rotor, so there's only one thing it's likely to be if it is spark related. I'm also going to replace the timing belt and check timing since I have no idea when it was last done.
     
  6. Jacob Field

    Jacob Field New Member

    Did some more research. Sounds like it definitely is worth not dropping the engine to redo valve seals, if that ends up being the problem. New seals are $38 and a compression tool is cheap on Amazon.

    Now planning to do the following:
    • Redo compression test, try the oil trick to see if the rings may be the issue
    • Bleed the coolant system
    • Try a DIY leakdown test (IE hook my air compressor to my compression tester tube at ~100PSI and listen for air leakage
    • Try a blowby test as well (probably won't tell me anything leakdown doesn't)
    • Try soaking the pistons with Seafoam or Marvel Mystery Oil over the next week while I wait for the new timing belt and other parts I ordered. I'm skeptical of it doing much, but enough people swear by it or say it's made a difference. People say it can help free up stuck piston rings, which based on my research could be causing the oil related symptoms I've been seeing. I did see an import shop guy say they see a lot of Mitsus with gunked up rings and I don't think it'll hurt anything.
    Then, new timing belt, new alternator/radiator fan belt (old one is definitely loose), make sure the engine is lined up, and try the iridium spark plugs I got. Hopefully that helps, and the leakdown test should help me figure out if it's valve seals or piston rings. If it's neither of those I'll probably go ahead and replace the valve seals since that seems to be a common issue and it's cheap.
     
  7. Bowe

    Bowe Member

    Not to discourage you but while it is possible to replace the valve seals with engine in place cylinder #3 is difficult to access in a truck atleast. If I was doing that job and timing/wp I’d think hard about just dropping the engine. Leaning into the “engine bay” gets old fast on either job.

    When you do timing belt pay special attention to the instructions for timing oil pump/counterbalance, follow it to a t or you get to tear into again like I did.

    I tried iridium plugs hoping they would be less prone to oil fouling so I could continue to use my truck before I changed seals but it ran horrible with them for whatever reason, switched back to copper plugs.
     
  8. Jacob Field

    Jacob Field New Member

    Huh, interesting that the iridium worked poorly. I've already ordered them, so we'll see how they do on mine :) Copper plugs are cheap though so no big loss.

    I'm planning on following the Toro manual for timing. It mentions an 8MM rod for the counterbalance and seems pretty detailed, which is a nice contrast to the sparse wording and grainy pictures in the translated manual I have.

    I already did waterpump with the engine in the bay (it did get old) but I'm young and flexible still, so... At worst I can drop the engine after I discover the valve seals are too annoying to change with it in the car.

    If I discover I have to do the head gasket though... That engine is getting dropped.
     
  9. Bowe

    Bowe Member

    I was dealing with so many different issues that the iridium’s likely will work for you but with oil fouling and carb issues they made mine worse.
    Funnily enough I have a “factory manual” and I still used the toro manual for reasons you state. It also doesn’t show the proper way to tension the belt so that’s super. My issue was I pulled the rod before putting belt on and that pulley spun, I lined it back up thinking it would be correct.
     
  10. Donald McRonald

    Donald McRonald New Member

    I can't offer any help but I appreciate this post. I've got a '95 U42V, seems like there isn't a ton of info on these specific models online. I've very little experience with troubleshooting motor vehicles and am trying to learn as much as possible.

    My van runs great generally but has an issue that's strange to me. It starts up right away from a cold start, but after driving around town for a bit, any subsequent starts are hard starts like you mention, cranking longer, pump the gas, etc. I've never had it fail to start completely but I've no idea where to start for the most obvious possible culprits.

    I have changed the oil/filter since purchasing, and have a fuel filter on the way, but that's it so far.

    Anyway, thanks again, I'll be following your posts and good luck with your van.
     

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