Intermittent No Start 3vze
 

Stopped at the gas station this morn, put gas in, went to start and no fire over.
Starter turns motor over, no problem.
Pop the hood look around nothing unusual.
Call the misses in preperation to bring me some tools, etc
About 15 minutes has lapsed, try starting and fires right up.
Drive it home, no issues, runs great.
Once home shut it off then restart, no issues
Try that a few times, no issues restarts everytime.
Go in house for 5-10min come back out to start and same issue, starter turns over engine fine just no fire.
By pass fuel pump and can hear pump running.,
Try to start with fuel pump bypassed, same issue
Have not been able to check for spark yet using timing light
Checked codes and had a stored 12. Check engine light never came on during operation. No G or NE signal is input to the ECM for 2 secs or more after STA turns on.
I have had a harder than normal restarting once the engine was hot and sat for about 20 to 30 min or more for sometime. Just took about 2 to 3 cranks vs 1 on a normal start.
Seems to be heat related
From a cold start she always seems to fire right up as normal.
Any ideas on where to start probing.

cheers
andy

What's code 12? (Seriously Andy, you're not the only one who does this. It seems many posters think that everyone on this forum has a perfect memory of every possible trouble code. YOU already looked it up. Help us out with "No G or NE signal is input to the ECM for 2 secs. or more after STA turns on.")

G and NE originate in the distributor, and many electromagnetics can be heat-sensitive. Start there. http://web.archive.org/web/201212070...12onvehicl.pdf Push-pull the rotor to feel for play; if you have a failed bearing that will give you wonky spark.

Vapor lock is another (slight) possibility. Carry 6mm (1/4") vinyl tubing and a bucket; when you can't start (hot?) plumb the fuel return from the FPR to the bucket and run the pump with the diag connector. If you have a fuel vapor bubble, either nothing will come out, or the bubble will get squished out and you'll be good to go.

But I'm guessing ignition. Since you have an intermittent problem (the hardest to find), carry your timing light with you. If it conks out, you can immediately check for spark.

Thanks for chiming in Scope. Apologize for the lack of code 12 explanation, I for one should know better for as long as I have been here. Have not been able to accomplish a whole lot today but did test the distributor (cold) across all 3 points and everything was in spec.
G1 - G = 182ohm
G2 - G = 183ohm
NE - G = 185ohm
Drove it around for about 10 mins to get up to operating temp and retested although i probably need a good 30+ min drive around.
G1 - G = 198ohm
G2 - G = 199ohm
NE - G = 205ohm
I will pull the cap tomorrow and check the air gap and look for any excessive play.

Also tested the secondary resistance of the coil both cold and hot. My multimeter does not appear to be sensitive enough to read the primary resistance.
Secondary cold = 13.3kohm
Secondary hot = 14.5kohms

​​​​​​Will take it for a longer drive tomorrow and get her heat soaked and retest distributor. The distributor that is in it now is approx 3 yrs old. New replacement, think it was a Rich Porter distributor. I do have my original OEM that i can throw in if necessary.
Also need to clear code and see if it comes back.

cheers
andy

Have been playing with it somemore this morning. Took her for a good 30 minute drive this morning to make sure everything was good and hot. Checked the distributor across the 3 points and nothing was higher than 215ohms. Checked coil also at 15kohms. Pulled distributor cap and checked for shaft play and all was tight. Ckecked air gap across NE1 .008in so everything looks to be in spec as far as distributor and coil go.
Checked codes again and pulled
code 12 No G or NE signal is input to the ECM for 2 secs or more after STA turns on.
code 24 Open or short in air intake temp. sensor circuit for 0.5 seconds or more THA
code 31 At idling open or short detected continuously for 0.5 seconds or more in VAFM circuit. Open VC. Short VC - E2

Cleared codes and tried to start. Turned over just fine no fire. Had timing light hooked up during this phase and was not showing any activity on timing light during cranking. So no spark.
piddled around some, about 5 to 10 minutes and tried to restart and she fired right up. Checked codes again and code 12 is back but not 24 or 31.
So any clues as to what to check next?? Possibly VAFM? I assume the Air intake charge sensor is built into the the VAFM.

cheersandy

My goto for electrical.. Voltage drop.. Typically at the fusible link. Some times just poor ground connection.

You have a group of sensor codes that all rely on the five volt reference sent by the ECU. Is the internal circuit faulty, is it wiring at fault. All pretty simple voltage checks and some battery system maintenance.

Revisiting this issue as I have yet to figure it out and I am clueless as to what I need to check next.
It is sooo intermittent which makes it hard to track down.
From what testing I have been able to do it is spark related. I did as scope103 suggested and keep the timing light in the truck and hook it up when it happens and I get nothing from the timing light.
Still getting the code 12 when it happens.
. Which is:
1) open or short in NE, G. Circuit
2) distributor
3) open or short in STA circuit
4) ECM
I switched out distributors today to see where that leads. I did test the distributor that was in it and i did not get any unusual reading, but switched them just in case. I listed the specs i got in an earlier post above.
When it is running it does great no issues what so ever.

cheers

A dirty, loose or just inadequate ground will cause all of these. So would a brown out during cranking.

The ignition fires independent of the ECU when the STArt signal is active there is no feedback from the ECU to your ICM. If the voltage is good, above about 10-11, during cranking and the distributor pick up is functional you may have a bad connection to the body ground at the ICM. How sure are you the signal wire is good and has firm connection at both ends, from the distributor to icm, check it iirc it's a low voltage AC wave.

I don't think that is correct (at least for the '93 and '94). There is no connection between the distributor and the igniter (I assume ICM refers to the igniter). The four signals from the distributor (NE, G1, G2 and IG-) go straight to the ECM The ECM in turns sends IGT ("ignition trigger"?) to the Igniter, which is what drops the "-" line to the coil, firing the spark (upon sensing the spark, the igniter then sends IGF back to the ECM).

Andy_A's problem is very unlikely to be the ECM, unless it has been abused (it's under a part of the windshield that could leak, but that should be apparent). The ECM is very candidly telling us that it's not getting NE or G. (And Andy_A has confirmed the result: no spark.) So I don't think the problem is in the IGT or IGF circuit, or the Igniter at all. Andy_A has tested the distributor coils, and swapped the distributor, so my guess is he has an intermittent short/open in the white red green black from the distributor back to the ECM.

Thank you both Co_94_PU & Scope for the replies. I have not had a chance to drive it yet after switching the distributor but will get back with results hopefully tomorrow.

Friday morning I repinned & replaced the connector on the distributor & the coolant temp sensor for the ecu, not the gauge one.. The locking clips broke off some time back so I thought it a good idea to replace them. I was hoping and praying that may have helped the issue but i ended up stranded in the walmart parking lot later that night for about 30 minutes then it fired right up like normal.

i have checked the main 5 grounds that I know of
1) negative battery to passenger fender
2) firewall to top of intake
3) driver fender to driver side head
4) passenger kick panel
5) driver side kick panel
all good

​​​​I dont think it has anything to do with the STA circuit since the starter turns over just fine, there is no "brown out during cranking"

Looking thru the fsm i found how to test the STA circuit but could not find anything for the NE or G.

i did have another known good ignitor laying around and tried it awhile back and as Scope deducted it is not that. Ignitor can be ruled out.

What about the coil guys. In my experience when they fail they fail, nothing intermittent. I know my secondary resistance is okay, both hot and cold, but my meter is not sensitive enough to measure the primary. Could something be going wrong intermittently on the primary side that i cannot detect because of my DVM? They are cheap enough 20 bucks but I'm not into the whole throwing parts at it. If I'm reading correctly what Scope posted above the answer is probably no.

Scope electrical diagnosis is not my strong point but always willing to try and figure it out if possible. For the green, red, black, white wires should they be visible coming into the ecu? Would be nice to test the wires at each end. Bad part is they have to be tested when the problem is "happening" .

The ECU has not been abused in anyway that I know of and i am the original owner of the truck. I have probably only had that kick panel off a couple of times in the 24+ years i have owned it.

I did recently have a problem with the sunroof drains on the passenger side, ie not the drains themselves but where the water ends up, the rocker panels. I guess over the years the drain holes along the pinch weld had plugged up and the water was backing up and wetting the carpet. Fixed that. I did not see any evidence of the ECU getting wet. I will definitively go in and recheck just to be sure.

The truck is totally stock and the only real work that has been done on it over the years is head gaskets and camshafts + suspension. Toyota did the first set of head gaskets and put in a new short block under the campaign, and I have replaced them twice since. I had a pretty nasty camshafts failure at one point also. Recently redid suspension but used all toyota parts except bushings which are now all poly.

cheers
an old shade tree mechanic:-)

Call me clueless Co_94_PU, but could you give a hint as to where I'm to look for this???

cheers

Oh that damn 3vze again. Very right the 22re uses a different system.

https://cimg4.ibsrv.net/gimg/www.yot...9f6cd7eccc.png

You might not have a sensitive enough meter for that either. It will be a tiny little waveform (ac) output by the distributor pickup coil(s) and sent to the engine computer.

Show us the meter you use, maybe it has a Hz function some could explain for you.

Beyond that you need someone with an scope that knows how to use. I'm not comfortable explaining how an amplifier circuit works.

At this point I can only go back to the plugs, the connectors inside them actually. Make sure your male parts are clean and the female side is tight for a reliable connection.

Co_94_PU,
Will post up a pic of my DVM when I get home in the morning. Nothing special, an old radio shack meter that I bought back in my Mustang modding days. I sure do miss that old rig. Nothing like the sound and power of that old supercharged 302.

The connectors to the coil & igniter both appear nice and tight when locked into place. I have used DeOxit cleaning spray on them every so often to make sure they are clean and free of corrosion.

Just replaced the connector on the distributor last Friday morning. Cut the old one off, crimped on new terminals, seals, and connector.

Cheers

Will get back on distributor results later on in the week. Need to make sure whatever result happens either good or bad are repeatable.

I forgot to clear codes and need to do that.

cheers

Just wanting to update. Well so far have not had the no spark issue (code 12) recur since switching out the distributor. Will keep testing.

Now im chasing another demon which started Thursday morning, the clutch is not disengaging. Arrrgh..........

cheers

Unfortunately i have not been able to do anymore testing over the last number of weeks. Clutch gave out and needs to be replaced, so i have not been able to drive it. Hopefully we will have some decent weather soon and i will be able to get it fixed. Sucks having to do the work outside in the elements.