85 720 stumble

[lego126]

Hey guys. Hopefuuly someone can assist me in this now ongoing 7 month issue. Long story short.. back in Dec. 13' on my way home from work, my engine started sputtering. I've had the truck for 2 years only trouble has ever been the aftermarket fuel pumps until I got an OEM. I've checked everything, rechecked it, removed everything, plugged vacuum lines, put them back on... etc. I'm bout to roll it off in the river. I am gonna try something today I read on another post, about using jumper on neg. Terminal of ext. Coil. I'm getting fire. I've got the FSM. There are a couple things I gonna try today, I will let u guys knows. I gonna recheck my valves. And my cam timing. It idles perfect, revs good., sounds golden until while driving and its under load, up to about 2400 rpm. Then it feels like its hit with nitrous, and drums like a scalded dog

I've made it this long by have vac lines remained and plugged and and driving with my foot on the floor. I think the sputter starts around 1200 and only under load, and goes away around 2400-2800. Any help appreciated. I have NoT done is remove/clean carb. I don't wanna do that if at all possible. 85' 720 2-wheel drive 190k, 5 speed, all original except interior lights. B-) I do still drive it back and forth the 10 miles to work, but its steadily gotten worse it seems.

[datzenmike]

Check plug wires go to the correct plugs. There are 8 so easy to mix up/

 

Set timing to 3 degrees BTDC

 

Check valve clearance... 0.013" on all

 

Pull coil high tension wires off the dizzy cap and put an old plug in the end. Lay on grounded surface and crank engine. Do both coils fire?? If exhaust coil not firing replace the first fuse on the left hand side of the fuse box and check again.

 

 

If this does not fix the problem you likely have a part plugged primary jet and why the problem goes away once the secondery comes in.

[lego126]

I've done all those things several times. Last night before work, I jumped neg terminals together on ignition coils, and drove 5 miles to work... OK 3 miles. Not once did I get a spitter. The best its driven in months. Then this morn on the way home I drove around a bit just to give it a little more time. There were a few sputters but almost in noticeable. So when I get home I decide to remove the wire, and see what happens. .. no change.... still a slight sputter. So hooked it back up, and started troubleshooting again. Right now I'm gonna get some sleep, cause that #@$% truck has kept me awake til almost 1230 and I gotta work tonight at 7. But when I look down into the carb primary side, I can see glass being squirted in. Kinda like a water bottle, with your finger on top, squirt squirt, squirt. No matter what I do to outside variables, remove individual vac lines, unplug spark switchers, timing, there is still a flat spot. As long as I'm INCREASING the throttle even in the smallest amonunt,it will keep spraying, but as soon u try to hold it steady, it starts. I just sea foamed it before coming in a few min ago, maybe it'll help by tonight. One more question,, what exactly controls my vacuum strength in my intake? Like how much vacgoes to the top of but what deterkines the amount and what causes the increase. Any help appreciated

.the AB valve, o. How much goes to vacuum advance? I know it increases when accelerating, but my seems to have a lot,

[lego126]

Thanks for all the. Help and sorry bout typos, noddin off and 4 in. Cell phone screen.

[lego126]

Well after driving to and from work tonight I seem to improved the problem, but there is still a slight miss. Today I'm gonna pull off the valve cover and see what's going on inside there, hopefully nothing serious. I'm not sure if my alternator light has anything to do with my ignition, but its been on since I've had the truck, and never had battery troubles.its just barely visible even beside the orange glow of the sensor light. As I said in the OP, I did pick up a 86 FSM on eBay for like 30 bucks or something. I can't believe how much info is in there, I've never took Tue time to figure out why its on, I just assumed it was from mice living it where it was parked behind previous owners house. Thanks guys

[datzenmike]

Intake vacuum is highest with the throttle closed and drops as you accelerate. It's even higher (briefly) when decelerating.

 

Vacuum advance is always zero at idle but comes up off idle and roughly follows the intake level. The distributor 'feels' the vacuum but does not use it or leak it so does not affect the intake vacuum, at least it shouldn't if the hose is good.

[lego126]

I think I've jumped time. I pull cover off the adj valves which werea little off, but judging by the marks on the chain(silver link) and the dots on can . My cam dot at 12 clock and my top 2 dot at roughly2 o'clock. My silver link is 3 teeth down to the right of where it should be. It looms like the OEM chain and this would explain a lot of my issues. I've also got a 97' with the KA, I've had the hole in cover rebuilt motor so I'm sure I can fix it. Just will need so.e time. Thanks much for help Mike. I'll let u know how it goes, but one thing I'm sure I'll need help with, the oil pump/ dist. Alignment, is it the same as the ka? Thanks again for the help.

[lego126]

I'm unfortunately gonna have to drive it for a few more days the way it it, because m. Wife's forester got blown head gasket, so she's driving the 97'. But where it runs best is dist timing well past 20 below, more like 35-40 BTDC. Or should I TDC #1, and pull dist/ oil pump, and try turn alignment of them? Like I said its only gonna have to get me another 10 miles at most. I will be able to fix it Tue, just will need work and back 3 miles Fri sat and sun. What u think?

[datzenmike]

The bright chain links and the cam and crank sprocket alignment dots only applies when installing them for the first time. After the engine has been turned the alignments are random. Maybe every few hundred turns it may line up again???

[lego126]

Really?? Cause after turning it by hand for a certain period, maybe 4-6 turns it would wind up back at 3 teeth off, hmm that's interesting, but I'll have to do some more reading. The pattern seemed to repeat its self after a few min

[Charlie69]

If your charge light is dimly lit your alternator is probably not charging.  This could cause a lack of power to the coils.  Are you running your stereo , AC, and headlights?  Check your alternator.  O'reiley's or auto Zone or Napa can check them installed in your truck.

[lego126]

Alternator light has been on for years. I've had it checked several times, its always checked out OK. And it ran great up until about 7-8 months ago. The batt light does brighten and dim as I rev the engine. There is a black wire coming off the back of the dist that's been cut/ unhooked, I can't tell where its suppose to go. Its worked well since I've had the trucklast several years.

[lego126]

Something I've been wondering, what is the sensor/ switch that's just behind my water tempo sensor? Its got a green plastic connector, with a metal clip style thing securing it to the intake. It looks like a detonation sensor, but mine down at have a detonation sensor controller. If I need to post so.e pics, just let me know I'll be messing around with

Today

[datzenmike]

Really?? Cause after turning it by hand for a certain period, maybe 4-6 turns it would wind up back at 3 teeth off, hmm that's interesting, but I'll have to do some more reading. The pattern seemed to repeat its self after a few min

 

May be 4 to 6 turns but the point is that once turned it dosen't line up or only randommly.

 

Something I've been wondering, what is the sensor/ switch that's just behind my water tempo sensor? Its got a green plastic connector, with a metal clip style thing securing it to the intake. It looks like a detonation sensor, but mine down at have a detonation sensor controller. If I need to post so.e pics, just let me know I'll be messing around with

Today

 

If on the intake it's not a detonation senser. Only the Z20 engine had them and it was mounted on the block. Likely a coolant senseor for the feedback carb. Tells the ecu how warm/cold the engine is to set the mixture. 

[lego126]

Yes I think so as well. It isn't green connector its yellow and yellow/green and yellow/blue wire. Its connected with the same connector that my injectors are on my ka. Little metal clips that keep it in place. I knows its not my temp gauge cause I've unhooked the one in front of it and its like 1 inch in front of the one I'm talking about. This truck drives me crazy. I finished the timing chain every things hooked back up and running loads better. Turns out my tensioner spring was severely worn. Its a lot better hut I still have some cqrb issues. For instance I kept watching the sight glass on carb bowl. It was good but after not working on it for several days I noticed it starting to empty. Fuel is leaking down into manifold thru primary or secondary. And after readjustment of the valves now #4 cable is really ticking. Prob been increasing over past year from fuel slipping by. I could use a carb job and valves.

[sal]

Man I though I had problems with mine. That sensor you are talking about is the one that tells the computer the temperature.

[lego126]

Yeah I've got a few it seems. And a cracked head o. My wives Subaru that she's on Me about!!!!

[lego126]

OK so I juat finished rebuilding the carb. Wow there were define toy some clogged passages. I got it back together drove it down the road, lots better. After letting it warm up in the driveway, I hooked up a timing light, I noticed my timing was about 2 btdc. Hmm vacuum adv still hooked up it would normally by at around 12 btdc and 2 unhooked. So I checked the vacuum lines, all good, then right there at the very bottom of the carb where vac advance plugs in at I pulled the vac line loose, almost no vacuum at all. I refer the motor several times while checking vac on that line, I have good vac while revving, just 0 at idle. Is this normal??? I know the truck has always had vac before. And like I said anytime check timing with it hooked up it would add/subtract roughly 10 degrees to the timing. Any thought? Thanks much. I know when I put it back together I did have to readjust a few things like fast idle, vacuum unloader, but I'm pretty sure I got it all perfect.

[datzenmike]

Around the late '60s, all vacuum advance converted from manifold to ported carb vacuum. The port on the carb is above the throttle plate and senses no vacuum at idle. Once above idle, the throttle plate rises above the port and intake vacuum is applied. If your idle setting is too high it will mess with your timing setting. Generaly you do not need to remove the vacuum advance hose as there should be none to wory about. If you do remove, you do not need to plug the carb end as the port does not 'leak' vacuum.

 

Why no vacuum advance at idle??? Pollution control. The less air in the cylinder the more advance you need. Full throttle= almost zero vacuum advance. Normal idle manifold vacuum would advance the timing to 18 to 20 BTDC. This is where the timing would love to be at idle. Next time you are setting the timing at 12 degrees, try turning the dizzy clockwise to advance. What happens??? Right away the idle speed increases!!! because this is what it wants. The EPA mandated zero vacuum advance at idle to in effect run the timing retarded by 6 or more degrees. This reduces cylinder temps ansd pressure and reduced oxides of nitogen as well. It also makes for a very inefficient idle and much of the exhaust heat is absorbed into the cooling system.

[lego126]

I've only driven probably 8 miles total, but acceleration and idle are smooth as butter.actually amazing as to how smooth it feels.only one question though. Idles great, acceleration great, but while making sure everything was tightened up this norm after work. I was holding throttle around 1200-1400 roughly, and there is a slight surge, only slight, say its suppose to be at 1200, it will surge to 1350, then down to 1200, 1350,down to 125. I don't feel anything while driving, it s not doing it then at least as far as I can feel. It feels like the B.C.D.D. is off omething. Anyone know what coupd cause a slightly surge like that?? Thanks much!!!