3VZE cranks, but no spark... where to start?

[bajadulce]

V6 3.0, the truck just died on a small test run to the gas station and back. Now the engine won't start and will have to tow it home a mere 1 block away later tonight.

Check Engine Light is NOT coming on. Checked EFI fuse, and a few others under the driver side kick panel + had an extra EFI relay from another car. The car is turning over strong. All the lights and instruments appear to be working. I jumped the FP-B+ terminals on the diagnostic check to see if the fuel pump was working, and I could hear it working. Guess I'll have to pull a spark plug and check for spark tonight. I don't expect to see one tho. What would be a good place to start isolating my troubles?

[WME]

Check for spark,if you have spark then check for fuel pressure at the injectors. Read plugged fuel filter.

If you can't check fuel pressure then short spray of starting fluid on the air cleaner

[bajadulce]

Thanks WME.

Ya, no spark. But I did find a thread at YotaTech of a guy that is having the same issues. (NO CEL, NO SPARK.) I responded in that thread as well here:

3vze not sparking & Check Engine light not working

I actually pulled my 16pin terminal on my ECU as he described in that thread, and the car fires up but runs terrible as would be expected. I guess I should check all my grounds tonight and read more about this fellows problem as well.

EFI fuse is working + terminal getting power.

IGN fuse is working + terminal getting power.

Car starts/CEL works if 16pin on ECU is pulled.

Any ideas what I should check next?

Edit/Update:

I found that if I unplug my AFM, I get a CEL and the car starts (you have to jump the fuel pump as the AFM is now "unplugged"). Do I have a short somewhere or is my AFM bad? And what does my AFM and the 16pin @ the ECU have in common?

[WME]

Sorry Dude your beyond me. I'm a 22RE kinda of guy.

[bajadulce]

well thnx for the support and help anyhow. The 22r "e" has all this same stuff tho, just a bit different configuration.

EFI is pretty bullet proof, but when you have problems, it can sure send you for a loop. I've been really fortunate with all of my fuel injected cars and never had any electrical component problems other than a worn out dizzycap, rotor, or plug wires.

In a way, I'm glad all of this crap is happening right now and forcing me to learn about how the computer and fuel/ignition delivery work together. I would hate for these things to happen 50 miles on a dirt road in the middle of nowhere.

If there's one no-brainer thing I've picked up from this, is that if you don't have a CEL when you turn the key on, you're almost guaranteed not to have a spark.

I'm going to test the specs of the AFM as per the FSManual and go from there I guess. Too bad my 22re doesn't have the same AFM box. That'd be an easy test.

[bajadulce]

UPDATE Problem Solved!

Well today I grabbed my multitester and started looking at the specs of the AFM and it was definitely out of whack. Knowing I'd prob have to replace it, I went ahead and popped the silicone on the cover to have a little look inside....

Apparently a small thin metal tab had broken off of one of the leads and was actually laying across 2 terminals. As soon as I removed the loose impediment, the CEL (Check Engine Light) came on and car started with no problem.

Here's a picture of the tab shorting out these two terminals. (Circled in red.. a bit hard to see)

Here's a picture of the culprit.

Crazy to think that this little broken tab would keep the car from starting.

It looks like it broke off the 2nd to left lead, but can't seem to decipher where it might go? At any rate, I'm going to get another AFM from the junkyard to compare to and see if I can't repair this one to keep in the car as part of my EFI emergency repair kit. So far I have an extra EFI relay, ECU, ignitor/coil and potentially a 2nd AFM. I think that about covers the EFI, and hopefully I could limp back to civilization with these spare parts. TPS maybe?

3VZE AFM Tweaking

Also, here's an interesting thread at yotatech that describes tweaking your AFM for increased performance as opposed to the Supra swap mod. You can lean the mixture out a bit or rich it depending on what you need. richer to combat pinging I would suppose? Leaner for more performance slight gas mileage boost. I think I'll just leave mine the way it is, but its worth checking out reading.

[WME]

Good on you mate....

My factory 22re book has no jumper short cuts. Its just ohm and volt checks for the sparks.

[Tom W]

(Cold start problem sort of) Mine had a plugged Cold start Injector and no problem starting down to 20 degs or so after I got it cleaned and checked that it worked when cranking, I didn't notice any difference starting maybe it not needed that much. I had a VW with the extra Injector for starting,ended up putting switch and only using it in cold weather, it seemed like it flooded it in hot weather somewhat.

[Gulfstream Greg]

Here's a picture of the culprit.

Crazy to think that this little broken tab would keep the car from starting.

Maybe it's just been floatin' around in there and goes to nothin' and murphy kicked it!

[bajadulce]

Greg,

Ya I hate that Murphy guy!

I couldn't wait till Monday nor wanted to spend money on another part if this one is fine, so I popped the lid to my 22re AFM to take a peek. Both are nearly identical except for a different pickup for the flapper vane itself. I now see where the tab came from tho. It looks like each of the leads have angle-shaped ends. The ends are soldered to the circuit board and this second half loops back around as part of the lead itself. I'm sure there's a reason for this design, but that section of the lead just broke off. Maybe a prior owner had undid the 2 screws and tried pulling the circuitry out before? Who knows. The tab probably wasn't completely broke off and more likely was just hanging on by a thread and leaning over onto the other lead causing a short.

The AFM checks out fine to spec now and so I don't see any reason to replace it. The other tabs look fine as well.

@Tom W:

Interesting about the cold start injector not doing a whole lot. In my case, a temperature sensor has been sheered off. Probably when we put the new cab on top of the chasis as it is located really really close to the firewall. This sensor prob tells the computer to do certain things to the car other than just fuel. I have to fix it tho to get the car smogged as this sensor is throwing my Check engine light. Did you have an air-cooled fuel injected VW?

[Tom W]

Overall this has been a good post hope I can remember some of it when mine does something similar. The VW was Rabbit Also had a 68 bug with a carb dunebuggy

[bajadulce]

Well I doubt many ppl will ever have problems like this as these things are pretty bullet-proof. Another truck owner at Yotatech.com just coincidentally had the identical problem, so it does happen! His contacts actually arced across one another and thus threw his ECU off preventing the car from starting.

You can read more about it and see his much crisper pics here:

http://www.yotatech.com/f116/3vze-not-sparking-check-engine-light-won-t-come-190314/#post51233798

I guess the big lesson I learned here is that if you have no Check Engine Light when you turn the key and the car doesn't start, it's very likely you have something not proper with your ECU, EFI relay, or EFI fuse. In our case, a short in our AFM was throwing our ECU.

Also if you're having fuel issues, it's possible you have an AFM issue as well. When the flap opens, there is a contact switch that closes and turns on the electric fuel pump in the gas tank. You can hear the pump working if you remove the air cleaner top and move the flap. So this AFM box is quite an important part.

Well, I'm off to the junkyard to get that water temp sensor and then hopefully get this thing smogged. I hope I never have another EFI problem again.. that was not fun.