13Swords

Firstly, I want to thank everyone who has posted to Yotatech for all of the info; it's been a great help to me. But right now, I've got a truck that just will not stay running. Some background and details on what has been done so far.

I've had this truck for 18 years & it has been my daily, so it has run before without much of a problem. A few months ago I was having fuel issues (carb & rust pinholes in gas tank) & some backfiring problems (thru exhaust pipe & sometime thru carb). At this point I decided to do some restoration on the fuel & ignition systems. (more later)

After having done everything I will list below, the current problem is that the truck will start, run for 5 to 10 seconds, then just cut off. It will restart right after this, only to repeat the cycle. One interesting thing: just before the engine is about to cut out, it speeds up on it's own, WITHOUT pushing the gas pedal down any further, then cuts out. Frankly, I am now stumped & am not sure what to do next.

Below is a VERY detailed list of what has been replaced, fixed or otherwise repaired. Sorry for the length of the list but I want to be as complete as possible. All work done by me & triple checked (I'm overly careful when doing vehicle repair; if I don't know how I find out, no half-baked stuff for me). Any ideas at all will be appreciated. Thanks!

Repair/Replacement/ Testing List:

FUEL:
- NEW Airtex Fuel Pump with new strainer filter & flange O-Ring. NEW screws for flange (6).
- All electric connections to fuel pump clean & tight, including ground. Wires replaced with new.
- NEW fuel sender installed w/new wires, good connections; no physical interference with fuel pump.
- Gas tank clean inside; has grey sealant on inside in great shape, no rust found. Pinhole rust-thru on front of tank above mounting flange. All holes located, metal cleaned of all rust, entire area patched with PC-7 Epoxy Putty, allowed to cure 7 days before reinstalling tank.
- Gas tank pressure tested w/compressed air & soapy water; no leaks anywhere.
- NEW mounting hardware for gas tank.
- NEW filler neck hose & vent hose w/new clamps.
- NEW rubber fuel lines & clamps in all locations where needed; NO old lines used.
- Steel fuel lines inspected thoroughly; no rust or leaks.
- NEW fuel filter in engine compartment.
- All steel fuel lines were blown out with compressed air, in both directions, during tank overhaul; all lines clear.

- NEWLY REBUILT Aisin carb from National Carb. NOTE: This is the correct model carb for this truck (with "water choke") & was FUNCTIONING & driving FINE for a full month BEFORE the backfiring problems started. (!) NEW carb base gasket used on install.

Truck has been desmogged. Running vac advance to distributor with new vac line & I was running vac to power brake booster, but have now disconnected it due to suspected vac leak in booster. All other vac ports on carb are tightly plugged with quality rubber vac caps.

While truck was still running (with backfire problem) I did several vac leak checks w/carb cleaner (went thru 4 cans!!!). I can find no vac leaks anywhere, including carb base & intake manifold flanges.

- NEW PCV valve & hose. No vac leaks.

- NEW Timing chain & gears installed about a year ago. I pulled the valve cover & adjusted all the valves to spec., & checked the timing chain. Chain still taut with no slack or slop. Gear still looks new. Wear patterns on cam lobes look OK, nothing unusual, no wear "valleys" seen or felt. NO broken rocker arms, springs or valve stems; all look & feel OK.

- NO coolant leaks anywhere.

- NO exhaust leaks. Replaced exhaust manifold gasket & donut gasket in downpipe with new gaskets. Manifold nuts torqued to 33 ft#; have rechecked several times, all good.

IGNITION SYSTEM:

- Stock igniter replaced with NEW GM HEI unit, Standard T-Series # LX301T (Made in USA!). Properly attached to AC Delco heatsink & VERY well grounded.
- All wiring is new 14 gauge with crimp connectors & shrink tube, fabricated by me. All wires continuity tested before install, all good.
- NEW Ignition Coil Spectra Premium C624.
- NEW Distributor Cap & Rotor, made by Wells
- NEW Distributor Unit, remanufactured by Cardone
- Air gap on distributor pickup checked; correct @ .008".
- Confirmed distributor installed correctly; #1 cylinder at TDC compression, rotor pointing to #1 spark plug tower.
- NEW Ignition wire set by BOSCH
- New Spark Plugs by Denso; properly gapped to .031".
- Spark plugs torqued to 10 ft# per manual.
- Verified all wires connected firmly.
- NEW Ignition switch Standard # US117.
- NEW Fuel pump relay. Socket terminals cleaned.
- Tested fuel pump resistor; in spec @ 2 ohms.

MISC.:

- Battery good: 12.7 volts
- Cleaned & reconnected all grounds in engine compartment (3 on pass. side, including battery ground, ground at voltage regulator on fenderwell, ground connected to tab on cylinder head drivers side near firewall).
- Cleaned battery terminals & installed NEW terminal clamps. All connections tight & clean.
- Checked all fuses; all OK. No corrosion on fuse ends or fuse holders; holders cleaned with steel wool, no steel wool threads left behind after cleaning.
- All dash lights are working. All external lights working.

All new parts are less than 3 months old & have less than 2 hours run time on them total.

That's everything from my notes & what I can think of that's been done. Hoping someone knows what this is and can help. Thanks again in advance.

13Swords

A short follow-up. After doing yet more thinking on this (owie, my brain!) I am now leaning towards a bad voltage regulator. I had assumed that the fuel pump relay was the culprit, as it was 38 years old & the contacts were VERY pitted, which is why I replaced it. But now I find out these old external voltage regulators are basically double relays in a box, & mine looks original. Yet more electro-mechanical stuff that is likely failing. Will update if I find out this is the cause.

millball

Electric fuel pump on 1978 carbed engine?? New fuel pump relay??? WTF????

That being said, running faster, then dying, sounds like a fuel starvation issue to me.

Probably NOT gonna be the voltage regulator.

83

A lot of the 20R engines did have electric fuel pumps. Strange but true. My 78 had one.

13Swords

Yes, according to my research, Toyota switched to electric fuel pumps on the pickups starting in 1978 (last year of the first gen trucks). They also used carbs on the 22R all the way up to 1995. Apparently you could get a carb'ed truck or order the 22RE engine (fuel injection).

Will have to look into the fuel starvation idea, but given that everything in the fuel system is new & confirmed functioning parts I don't think it could be that. Another reason for me thinking this: before 2 days ago, the start and stall thing wasn't consistent in time frame. Meaning, it would start then stall 10 seconds later OR start then stall 2 minutes later; always varied. When I first put the new fuel pump relay in, it started right up and ran for 20 MINUTES before stalling out on it's own. If it was always 5 or 10 seconds, I could see how it was using up the fuel in the bowl & then there is no more gas, due to not being fed by the fuel system, but it always starts right back up after stall WITHOUT touching the pedal to give it a "priming shot".

Plenty of gas in tank. Can hear fuel pump running, no cut-outs.

Also 1 thing I forgot to list: NEW (not rebuilt) starter installed, all connections clean & tight.

millball

i've seen plenty 1980s' vintage carbed trucks with mechanical fuel pump on the head.

Anybody know when they switched back to mechanical, from the early electrics??

Charleslocke

My '78 protects the engine by disabling the electric fuel pump if the engine isn't receiving sufficient oil pressure---any chance that might contribute to your problem?

13Swords

Excellent thought, but that was addressed with the new fuel pump relay. On doing research, the oil sender is connected to the fuel pump relay & acts like a "circuit breaker" for the fuel pump, if the key is on but there is no oil pressure, engine running or not (stall due to crash, etc.) The oil sender is just like a switch: normally open with no pressure, closed @ 5 PSI or higher. Oil pressure falls off, switch opens & breaks the circuit to the fuel pump so it stops pumping. Because there is a relay involved there's a little more to it than that, but the basics are there.

Considered that the oil sender was wonky, but it appears to be functioning the way it should. Oil Light goes off within 1 second of start-up, comes back on 2 seconds after stall-out. No flickering.

13Swords

UPDATE:

Well, I got the new voltage regulator installed. Truck starts up fine & quick, runs well @ high idle. No more 10 second stall out. HOWEVER....

Once up to temp, she won't low idle without missing & trying to stall or actually stalling out. Stall pattern is a little different this time around; there is no "RPM zoom-up" just before stalling like before. I have a see-thru fuel filter & it stays full. I can even see fuel coming into it from the pump side port, so I'm thinking not a fuel supply issue. Could be the idle circuit in the carb I guess; will have to pull out the mixture screw & shoot the hole w/carb cleaner & see what it does.

Really can't understand how a basically new carb could get the idle circuit plugged up tho. No trash in fuel, new lines, new air filter, new fuel filter (old one was only a month old but replaced anyway).

Other thots are: alternator bad or going bad, shorted plate or plates in battery. Dunno.

13Swords

A little disappointed with lack of replies but will continue to post updates for anyone else who comes along later with similar problems.
Many Thanks to those that did respond tho.

FURTHER UPDATE:

Went ahead and ran the truck again for a few minutes before it stalled out again 2 minutes later. Walked around to check fuel filter again & hear a bubbling/hissing noise from the battery. This means it is charging but how much?

Hooked up the volt meter & started her back up; charge started @ 14.2 volts & steadily climbed up to almost 17 volts within, say, 20 seconds. Shut down manually.

Could be a bad voltage regulator new out of the box, but wanted to check everything else out downstream, so to speak. Pulled the rubber cap off of the alternator plug, only to find 2 of the 4 wires were actually hooked up to the plug!

One of these (blue wire) is for "CHARGE" light on dash, which hasn't worked since I got the truck 18 years ago. Other broken wire was the "exciter" wire (green) that goes to voltage regulator. White wire, (battery feed) was intact, as well as the orange wire (attached to "B+" post terminal).

I've had 5 batteries in this truck in 18 years (about right for Florida, heat down here kills em faster) & never a charging problem. I did check battery before volt meter test, read 12.62 volts; cranks engine over fine.

So, pull both battery & ALT & take to Advance to have them tested. Battery tests mostly OK, if a little low on cold cranking amps capacity (413 amps read, rated @ 550 amps. It's an Interstate battery that I got from a junkyard 2 years ago in good shape; no idea of previous usage time.

ALT came back from test DEAD. Guy said he tested it 5 times & it's not throwing out ANY VOLTAGE at all. Guess I fried the diodes on that last test. How coincidental. I do know the guy well from previous dealings so I don't think he's lying just to make a sale. IMO.

So, have a NEW battery waiting to go in, & a reman'ed ALT on order due in tomorrow. $117 for both after July 4th 20% off deal; not bad sez me.

Still have to figger out what to do with the ALT connector tho. I have found a few replacements online & will post em up in another thread for those who are looking for them. I am likely to go the crimp-on spade lug route as I have those on hand and know which wire goes where.

More to come.

highonpottery

iTrader: (1)

I'd ask over at toyotaminis too if you haven't found that site yet.

I replaced the alt in my 78 a few months ago with a GM alternator. It was very simple and I think with the TG bracket it's still cheaper than the one you mention or very close to but almost twice the output. You can fix the wiring you've got and install a new alternator but you're still using a tiny 10-12ga wire in the stock harness to move all your power - no thanks! I have a thread over on TM listing what parts I used - username Perkolator.

83

All my 80s 22Rs had the mechanical pump. It was only the 70s 20R that I've ever seen electronic pumps on.

13Swords

Perkolator - Many thanks for the reply & input. I have also looked around quite a bit on ToyotaMinis; it's been helpful.

I considered the GM ALT mod but decided not to do it for a few reasons. The Toyota Parts are more of a direct replacement; I have done other mods on this truck just to keep it going & I'm kinda tapped out on doing more of it. Just a personal choice to limit the work load & abilities load, if you know what I mean.

Reason 2: I don't really need twice the charging output because the trucks' stock demands aren't that high to begin with; just lights, ignition & electric fuel pump. I don't even have a working radio going on 18 years & no plans to add any electric accessories at all, so I figure the stocker ALT should do OK. Plus, price is the same with less work for me; bonus!

I did check the wires; they appear to be 14 gauge to me, same as I used on the GM Ignition module job. Last I checked thats good to 32 amps; sounds OK to me given the stock ALT is rated at 45 amps max, but then again some might disagree, I guess. Will certainly consider it further.

Thanks again for the info & your time.

highonpottery

iTrader: (1)

It's your choice, just letting you know it's not hard or expensive to do the upgrade. Oversize wiring and more power output available is always better IMO even if you don't use it. I know there's no real draw from how little electronics are on these trucks (I laughed at the puny wire harness first time I looked under the dash) but I plan on adding an amped stereo eventually as my only real addition to the truck unless I get the urge to drop the $ on an aftermarket AC kit, which will have a decent draw. Also I already had the TG alt bracket in my parts box from the PO.

13Swords

So, yet another update.

Got the new alternator & battery installed ok. Truck fires up immediately & runs ok at high idle. Charging system all working fine, according to volt meter readings. I ended up going with crimp-on spade plugs & they are working ok on the alt. Just had to tighten up the sides a bit for more grip, to make sure they don't fall off of the lugs from vibration. So far so good.

So back to the idle problem. Once the choke opens up & the RPM's drop to slow idle range, the engine stalls out; absolutely refuses to run at operating temp at low idle. Will restart immediately & keep running if you hold the gas pedal in some, but if you let it go to idle position it stalls out right away.

While it was running at higher RPM, I noticed that the fuel filter underhood was only half full, and that gas was only sporadically dribbling in, with the occasional "glug". So, another fuel pump is going in (Airtex E8188). Luckily, Airtex has a lifetime warranty on their fuel pumps, so it's only going to cost me $7 to return the old one; new one ships to me for free. About a $53 savings. Gotta love warranties.

Got the new fuel pump. Blew out & cleared the fuel feed & return lines for the 4th time (all clear) & installed the new pump (2 more hours work). Truck starts up right away, fuel filter is full & you can see steady fuel flow into the filter; much better than before.

Only problem is that, it didn't solve the idle problem!
Truck runs fine @ high idle but once it get to full operating temp & choke is open, it still won't slow idle. Just dies off like before. So there's still a fuel problem somewhere, and I do have thots on this; more in next post.

13Swords

UPDATE:

So, time to take stock of what I have done, methinks. Wayyyyy too much time & effort has gone into this for the truck to not be running & drive-able.

After reviewing everything I've done, I put my finger on the desmogging I did to the truck; in particular, the charcoal canister. Desomg threads I have read here & elsewhere don't always agree on keeping or pitching the canister, but I decided to keep mine. I had it inline with the fuel return (as stock). The only difference being that I hooked up a vac line from the canister to the carb for fuel vapor purging purposes.

My thot now is that maybe the canister is too restrictive or clogged up (altho I DID test it with compressed air & it did not seem to be clogged, in either direction), & was maybe causing a fuel starvation problem @ low idle. So out the canister goes. I hooked up the rubber fuel return line from the carb to the hard line going back to the tank. Basically the same hookup as before, but without the canister in the middle of it all.

It made almost NO DIFFERENCE AT ALL.

The only difference I noticed is that it WOULD keep running @ full temp, but only if the idle speed screw was turned in enuff to get to at least 1000 RPM. When I had it set this way before with the canister hooked up, it would still want to stall out, even @ 1000 RPM. So, apparently there was some restriction in the canister, but it's still not the problem of not being able to get a good, steady, low idle.

Now given all of this, I'm thinking that the very last problem I have is a blockage or restriction in the carb itself, especially on the idle circuit side of things (idle passage, idle port, main venturi, main jet). How this can happen to a professionally & freshly rebuilt carb with less than 200 miles on it, that was working just fine before, is beyond me. Opening up the mixture screw for more fuel (richer idle mixture) still doesn't seem to make any difference at all, so I'm leaning towards some internal blockage.

Other possibility (and I admit this is remote) is that the carb is pulling more vacuum than before, due to the desmog, with all of the smog ports on the carb plugged tight, so it's drawing more air than the idle jet can keep up with(???) Maybe I need a bigger idle jet?

Since I still have some carb cleaner on hand, I think I'll just spray out the inside passages of the carb; basic & simple & no dollar, & see if that does anything. Will detail that & post results here.

13Swords

UPDATE:

Without going into too much detail, here's an update. After a VERY through INTERIOR carb cleaning (with carb intact) & nearly using a whole can of cleaner. The idle problem remains. No Change. Bowl was washed out, both jets sprayed out, venturis sprayed out, idle mixture passage sprayed out, inlet to needle seat. NOTHING, no change at all. For the record, very little "trash" came out of the bowl on the first washdown. About 7 or 8 VERY small black particles. I've washed MUCH bigger stuff out of perfectly working carbs before, so I would think there isn't a blockage problem in the carb, but I guess I could be wrong. Fuel level is right whaere it should be @ halfway up the sight glass, so the float, needle & seat are working right.

I can't take the airhorn off this carb; if I do I void the lifetime warranty that came with it. National Carb puts some "anti-tamper" goop on some of the airhorn screws and if that stuff is missing when you send it back to them, the warranty is out the window.

So this leaves me with a few possible problems. The carb has a blockage or restriction in the idle circuit. This I am finding very hard to believe. I have cleaned it as thoroughly as I can (twice!) & It's had at least 5 gallons of clean, fresh gas run through it during all this testing, over a period of several weeks. Truck is under a carport so nothing has "dropped into it" & the hood stays closed.

Other possibility that didn't occur to me until now. Still seems like a fuel problem, but I have an all new (or triple verified good) fuel system, right???
Not so fast. WHAT ABOUT THE STEEL FUEL HARD LINES??? They are ORIGINAL to the truck (38 years old). Maybe INTERNAL rust or corrosion in the fuel lines? I've blown them out at least 4 times before during all of this and they seem OK, but what if they are restricted (reduced diameter due to build-up on inside walls), like 30 or 40 percent of the diameter?

Theory goes like this: Runs @ high idle (1800 RPM) OK due to faster engine speed supplying fuel pump with higher voltage, therefore higher fuel flow than at low idle. But when idle drops @ operating temp (850 to 1000 RPM), voltage drops & fuel pump turns slower, supplying less gas? And that volume of gas isn't enough to keep it running at low idle? How weird would that be? Based on the RPM numbers alone, my math sez that's a 55% drop in RPM. Corresponding percentage drop in voltage???? Dunno.

So, I am off to go soak the insides of my fuel hard lines with alcohol for an hour or so, then blow them out & see what comes out with the alcohol. If I get rust or any good amount of crud, they are getting replaced with new. Since I am (obviously) keeping the truck & have already done all the other mechanical restoration, they should be done anyway.

Stay tuned.....
(Gawd, will it ever end???)

abeD85flatbed

IMHO the stock carbs are always suspect. A weber 32/36 is a much simpler carb and far more reliable.

highonpottery

iTrader: (1)

I would suggest you install a fuel pressure gauge/regulator just so you have a little more info and control.
On the plus side this truck is good to go for another 38 years once you figure it out

13Swords

"I would suggest you install a fuel pressure gauge/regulator just so you have a little more info and control.
On the plus side this truck is good to go for another 38 years once you figure it out."

Not a terrible thot at all, as more info is (almost) always a good thing. I'll consider going there if the new lines don't change the situation. However I think (dang, that's how I always get into trouble with this!) the new lines will finally get it sorted. Thinking back to a flow test after the 1st new fuel pump install, & the flow wasn't very impressive. I'm reading elsewhere that flow should be half pint to pint of gas in 10 seconds (8 to 16 ounces). At last check, I got maybe 2 ounces in 10 seconds. That's a reduction of fuel flow of 75%, minimum.

I'm also reading that low fuel flow lowers the bowl level, as it can't keep up with demand. Runs fine @ high idle w/choke on so it's rich enuff then, but as soon as the choke comes off, it leans out (more air) & the gas level in the bowl isn't high enuff to feed the idle circuit passage. Apparently, this passage opening is IN the float bowl. If level is below it, no gas to idle circuit, hence the stall out (nothing there to burn).

One thing is certain; I know TONS more about how all these systems work now, so future problems shouldn't be such a pain in the backside.

I'll take that plus of 38 more years!!! Thanks!

Will update on fuel line progress. Going with Poly Armour 5/16" fuel line by AGS. Look em up on the web; looks like great stuff, and versatile too. Works for brake lines as well.