1989 MM 2.0 Crank No Start

[smr1618]

Hey everyone, truck was running pretty well until I turned it off and it didn't turn back on 20 minutes later one night. Was curious if any of you might be able to weigh in.

For context, it is converted to a Weber and I believe the PO also put in a new fuel pump by the fuel cell when swapping the carb and installing a security system (low oil pressure cuts fuel pump). It was running well enough, I tuned the carb, replaced the cat, electrical (coil, cap, plugs), and belts when I got it. It was in time. Only things I have not touched that could use some attention are the valves and probably gaskets. It has been reliable, however after a 45ish minute drive one night, I turned it off and could not get it back on to move it after. Cranks, even runs very briefly but bogs out.

I checked plugs, it was running a little rich but I am getting spark. Fuel pressure gauge is reading 2.5 psi/I think I am getting enough fuel through the line. Some potentially relevant symptoms are that the coolant level was low. No proportional puddles underneath the car, few drops at most. I flushed the cooling system somewhat recently, no leaks either. Car also does not overheat, but runs somewhat hot in the safe operating temp range in some conditions. When driving, there is a rhythmic ticking/rattling that does not increase with rpm. I assumed it was a vacuum leak but given these other developments think maybe the water pump is going bad.

Given the security system the PO put in I thought maybe something was faulty and/or cutting power to the pump or the pump was damaged, but I am getting fuel pressure and I have oil in it.

Am I due for a new head gasket/resurfacing? Any ideas? Thanks in advance.

[smr1618]

Also worth mentioning that the PO did some things I do not fully understand with the vacuum lines on the intake manifold/the vacuum system was largely disconnected. I did all the previous work given its current state so it may have been potentially running well from a distance but not actually. If any pictures would help or there are any experts in the area that could lend a hand let me know

[smr1618]

Looks like there’s some weeping under the fuel pump. I’m guessing the fuel pressure regulator down line cause it to prematurely fail. Doesn’t smell like gas though

[SubGothius]

Did it eventually start after waiting a while longer? I've also had an occasional problem lately with hot restarts after it sits a little while, maybe up to an hour or two.

I think the issue may be heat soak causing fuel to percolate from the carb into the intake, causing a rich condition. I've been able to resolve the issue when it happens by taking the air cleaner off, hold the throttle open slightly, and stick a screwdriver into the carb to prop open the throttle and let the vapors dissipate out of the intake over 10 mins. or so. Thinking I might add a phenolic spacer plate where the carb mounts as an insulator, e.g.:

https://www.carburetion.com/Products...Part=99005.119

https://www.pegasusautoracing.com/productdetails.asp?RecID=34979

https://www.ebay.com/itm/201514203222

[smr1618]

I tried a couple days later with no luck. Tuned my carb to webers specifications and still getting a rich condition on my plugs so maybe I'm struggling with the same issue. I'll try your solution. You think its only from direct heat? ie if you had the spacer to insulate from the intake manifold you don't think ambient temperatures would be hot enough to cause it?

[SubGothius]

Heat is heat regardless of transmission method, so reducing heat transmission by whatever means feasible should reduce the problem, but I'd reckon conduction thru metal from the engine to the intake manny (which also has some coolant flowing thru it!) to the carb body is a more significant contributor than convection thru the air.

That said, sitting for a couple days would be far more than long enough for a transient flooded/rich condition to dissipate. Really I've only had the heat-soak flooding problem on hot days when it sits at least a half-hour or so up to maybe a couple hours or so. Shorter than that isn't enough time to flood the intake with enough raw fuel/vapors, and longer than that allows the heat and vapors to dissipate.

Also, I never touch the gas pedal while cranking on a hot restart, so the choke remains fully open, and the carb accelerator pump doesn't squirt any extra fuel in. Once it fires up, then I can feather the gas a bit if needed to keep it going and "clear its throat".

If you only tuned the carb by the screws, your jetting might be too rich. The Weber "idle circuit" actually covers both startup/idle and low-rpm operation up to about 3k RPM or so, and fortunately the idle jets are easy to access from outside the carb.

[smr1618]

That makes sense. Youll have to update me if the spacer fixes your issue.

Maybe the jetting is too rich. I think my e-choke spring was not on the peg attached to the cam actually as well so the tune might have been off. It is a 50/50 if I can start the car without a quick pedal tap so likely another symptom. I think my vacuum lines are wrong as well so the tune was even further off. Ill post some pictures

[smr1618]

https://imgur.com/a/rmnNSvS

Picture 1: Breather just has a filter, should this not be routed back into the air cleaner or to the charcoal canister? I have seen these both described as the correct method

Picture 2: Vacuum advance runs to the left barb on the carb, other barbs on intake manifold are capped

Picture 3: You can see where the vacuum advance connects to carb on the left, smaller hose. the larger hose is connected to nothing, it is capped with a cracking cap. The array of hose barbs below are mostly capped, with one short length of open hose on one of them.

Picture 4: EGR valve disconnected from anything, another angle on the intake manifold barbs from 3

Picture 5: More capped barbs underneath in the back

Picture 6: PCV valve going back into intake manifold

I would appreciate any help, all the OEM vacuum systems were disconnected from everything, save the gas tank line running to the charcoal canister

[FMS88]

Good pictures and very helpful.
Regarding #1, look at the bottom plate of the Weber air cleaner. If there’s a 3/8” or so port, remove the filter on the valve cover and run a hose from that port to the air cleaner port. If there’s no air cleaner port, leave things as they are. Don’t route it to the charcoal canister.
#2 and 3: The Weber instructions for the DGEV indicate the left vacuum port is for the EGR valve and the right for the distributor vacuum advance (see pg3 of https://www.piercemanifolds.com/v/vs...stallation.pdf ) The Mitsu EGR requires two vacuum hoses so connecting the Weber to the valve may have no effect or an adverse one. If so, cap the Weber port.
Also, the short hose on the manifold vacuum tree below the carb, should not be open. All those ports should be capped to prevent a vacuum leak.
Otherwise, the setup looks good.

[smr1618]

Thanks FMS, there is a plastic barb on the air cleaner, I thought that might be meant to attach to the VC. Sounds like the hoses on the vacuum port are backwards/the loose end should be capped. Good to know about the manifold tree, thanks. Ill give this all a try and re tune the carb if I can get it to start. Think there may be another underlying issue I have yet to identify. Appreciate the help from you two as always

[SubGothius]

Pic 1: Breather port is fine with just that filter; it mostly serves as an intake for air to replace crankcase vapors that the PCV sucks out, so the hose from that to the air cleaner would normally just feed it filtered air, which this filter cap accomplishes in your case anyway.

Pic 2: Looking at the two small barbs on the driver's side of the carb (in the orientation you have it mounted here), the right (rearward) one is for vacuum advance, and the left (forward) one is for EGR. If you're only using one of these, cap the other one off (the EGR one normally comes with a screw in the end to plug it).

Pic 3: That large hose in the foreground shouldn't matter, so the cracked cap on it shouldn't matter either. What's the other end of that connected to? If you've still got the stock carb's feedback control box mounted to the driver's inner fender, you can remove that and everything connected to it.

Pic 4: EGR is fine to leave disconnected.* EGR reduces combustion temps, thereby reducing NOx emissions, by diluting the intake charge with already-combusted inert gases from the exhaust that won't affect the fuel:oxygen ratio. That short length of hose on the barb tree should be replaced with a cap, or you could even hook up the vacuum advance hose to that barb for full advance at idle to reduce idle combustion temps*. Caps are prone to crack (rubber) or melt/shrink (vinyl), so IMO better to cap open vac barbs in pairs using a short loop of vac hose, which tends to hold up longer.

Pic 5: The only vacuum caps you really need are for any open barbs on the carb itself and anything on that tree of barbs screwed into the intake manny below the carb. All the other barbs aren't open to manifold vacuum and thus don't need to be capped.

Pic 6: PCV connection looks good.

* Unless your local emissions regs require everything stock.

[smr1618]

Pic 2/3: That loose hose with a cracked cap is connected to the right barb on the carb (where vacuum advance should be attached). Ill swap them and cap the EGR barb. I just removed the control box the day I made this post as it wasn't connected to anything.

Would you say it would be better to hook up the distributor vacuum advance line to the carb or the barb tree?

& Clever trick with the hose capping 2 barbs instead of using caps, may try that.

CA definitely requires that for visual inspections but I'm past that point anyways. Just trying to get the (semi) stock engine reliable and easy to work on while I plan out a 4g63t swap

[FMS88]

Would you say it would be better to hook up the distributor vacuum advance line to the carb or the barb tree?

Start with the recommended routing which is connecting it to the carb. Once you get it running well and see how it performs, you can change the routing to see the effect. However, I'd expect poorer above idle performance if using manifold vacuum because manifold vacuum decreases with engine speed and that would retard ignition timing.

[SubGothius]

Really the only difference between ported vs. manifold vacuum is that ported comes from just above the throttle butterfly in the carb and thus does not apply any vacuum when the throttle is closed, only when it's open at all, effectively disabling vacuum advance at idle. This raises idle combustion temps to reduce hydrocarbon emissions at idle.

[smr1618]

Good to know, thanks guys.

Update on conditions: Good spark and getting fuel on all cylinders. Not sure if too much or too little after resetting carb to factory and correcting vacuum issues, as it won't run. Compression is not so good. First 3 cylinders (from front to back) are returning ~125 psi consistently, while 4th cylinder is returning 175. I am not sure what one cylinder having dramatically higher psi could indicate other than improperly gapped or failing rings (carbon buildup would have variation but not that high is my understanding). The other 3 are also barely above the manual's recommended 119 psi minimum to rebuild so I'll likely just bite the bullet and redo the head. Oddly, my coolant and oil are uncontaminated from one another so it does not seem like a head gasket issue. Is it possible my valves are just way out of spec? I am also struggling to understand how this would tie into my truck running okay then just not turning back on. Have not visually inspected for cracks in the head/block/pistons

[smr1618]

I have not yet verified that the timing is still good, guess it's possible a belt slipped or something as well?

[FMS88]

I have not yet verified that the timing is still good, guess it's possible a belt slipped or something as well?

Yes. It's worth checking the ignition and valve timing. Have you tried using some starting fluid? Even with lower compression, it should show some brief sign of life if the ignition system is okay. The intake jet valves might be too tight and not seating completely causing the low compression. Check their clearances. All other valves have hydraulic lifters, so no adjustment needed or possible.

[smr1618]

Haven’t tried starter fluid yet need to pick some up still. It’s showing signs of life without it, stumbles briefly then dies. I had ignition timing perfect but worth checking again for sure. Probably gonna be doing valves and head gasket/redoing the timing after anyways

[smr1618]

Been removing all the after market electrical to simplify troubleshooting. With most of it gone and reverted to stock, I wanted to verify that the ignition coil is actually wired correctly. I have read through these two threads which outline the same topic thoroughly and, while the second one helped more with pictures (smooth brain I know), I am still struggling to understand fully. Electrical is not my strong suit, I would appreciate if anybody could weigh in.

My Coil:

https://imgur.com/a/NG1SjHy

Previous Threads for others who may not have seen them:

http://www.mightyram50.net/vbulletin...=ignition+coil

http://www.mightyram50.net/vbulletin...nd+S+Terminals

[SubGothius]

I think the wire in your photo called out in red labeled "Attached to IGN post on cluster" may be unnecessary, if that just connects that end of the ballast resistor to the (+) terminal on the coil.

The (+) terminal on the coil should have only one wire connected, leading to the same ballast resistor terminal where the black+red wire is also connected. The other end of the ballast should only have black+white wire(s) from the loom connected, plus the black wire to the distributor pickup. The (-) terminal on the coil should have the blue wire from the dizzy pickup, a tachometer wire (usually white?) to the gauge cluster, and a positive wire to a condenser (apparently missing in your case?). The condenser helps filter out RF noise from the ignition coming over the radio and also protects the ICM (integrated with the pickup trigger inside the dizzy) from the voltage spike that occurs whenever a spark fires.

I think that second forum link you provided mainly explains how/why to rig things up on an early truck to replicate the purpose of the stock black+red wire on later trucks. This bypasses the ballast during cranking to provide full 12v power to the coil, giving the spark a bit more oomph for initial start-up. For normal running after startup, power from the black+white wire goes thru the ballast resistor to reduce the coil voltage slightly, reducing stress on the coil and other ignition components.

[smr1618]

Didnt see this, just finished rebuilding the engine and putting everything back in. Having the same issue as before, although it sounds much healthier. Better compression, stronger spark, I am getting fuel as well. My guess is maybe the coil went bad? Have to remove and test, its basically the only electrical component I havent replaced other than the distributor itself (although I did replace it ~6 months ago). I am getting strong and seemingly consistent spark, so I am not sure how it could be that. Will double check all fuses as well. Weber carb is set to factory, maybe the jetting or something is off, or the e choke is faulty.

Regarding your wiring directions SubGothius, the wire labeled IGN post attaches to the negative post on the back of the gauge cluster in the cabin. It does sound like I am missing a condenser, but everything else sounds like it's correct. I have an extra wire for the electronic choke but other than that sounds accurate.

[smr1618]

Here's a video if it is any help to anyone in diagnosing

https://imgur.com/a/O02jl22

[smr1618]

Got it fixed, running like a dream. Last thing I tried naturally. Ignition coil I put in in December was bad, likely due to the aforementioned wiring problems with the choke running off of it. The cluster doesnt work without the wire attached to it oddly, not sure if it's the "ground" or what. But it's running. Thanks to everyone who had some insight to offer.