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Rebuilt 4a-ge has no spark

 
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Hasskarre




Joined: 19 Nov 2017
Posts: 7

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PostPosted: Sun Nov 19, 2017 8:25 pm    Post subject: Rebuilt 4a-ge has no spark Reply with quote Reply with quote including images

Hi every one

I am in the process of rebuilding a 89 N/A almost from the ground up. Part of the rebuild was swapping the old engine that made rattling noises with a completely rebuilt engine from another AW11.
The rebuild is complete and the engine is in the car fully wired/plumbed, etc.

The starter works, the fuel injection works (at least the spark plugs are wet), bit there is no spark, neither at one of the four plugs or at the cable from the distributor.

I tried to find the problem with the on vehicle inspection guide on page IG-4 in the manual, which went like this:

Spark test - No spark (duh)
Check resistance of high-tension cords - within max resistance of 25k ohms
Check power supply to ignition coil - ca. 12 Volts. I also checked the ground connection.
Check resistance of ignition coil - both primary and secondary within specs.
Check Resistance of distributor signal generator - All within 140 - 180 ohms
Check air gap of distributor - All within specs
Check IGT Signal from ECU - I figured out the color of the cable on the Igniter side but havent measured continuity yet.
But the test of the signal itself is not possible, since on FI-30 the condition for testing the IGT signal against E01 (ECU Ground) is only possible when the engine is idling.

But I guess the problem might be coming from there since one of the diagnostic codes I got is 12 - Rpm- Signal: No "Ne" or "G" signal to ECu when engine speed is above 1000 rpm, and the "Ne" signal comes from the Ingiter module.
The other signal I got is 41 - Throttle position sensor signal
And 51- but that seems to be for AC units.

Things I tried apart from the stuff mentioned above:
Check every fuse and relay in the fuse box in the engine bay (but in the ignition circuit only the engine main relay matters)
Check if the ecu gets power and mass for its corresponging pins under certain conditions (see FI-30)
Switch the ecu with two other models I had here (all three have different part numbers, I dont know the differences between them)
Try another coil
Try another mass air flow meter
Try different Relays
Try different Cables
Check if all cables are plugged in correctly (they werent at first, in fact plus and minus on the coil were swapped)
Other stuff I cant remember at the moment

The engine is completely rebuild.
I might have interchanged some parts from other AW11 (all 89, one german, one uk, one us with A/T), but all cables and connectors match.
I have re- checked if the distributor is aligned right when I checked the gap. I think I have it correct, but maybe it went one tooth to the left/right. Would that just give a bad spark timing or is that reason enough for the system to not engage?
Error code 12 might occur because the engine doesnt even reach 1000 rpm, I don`t know.
The distributor cap and finger are new.

Can somebody give me a hint what might be wrong? I am really running out of ideas.
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SuperRedMR2




Joined: 16 May 2005
Posts: 5486
Location: Wickford, Essex
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1990 Toyota MR2 Mk1b

PostPosted: Mon Nov 20, 2017 9:39 am    Post subject: Reply with quote Reply with quote including images

Have you lined up the cam pulleys and the timing cog behind the crank pulley?
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Hasskarre




Joined: 19 Nov 2017
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PostPosted: Mon Nov 20, 2017 3:33 pm    Post subject: Reply with quote Reply with quote including images

When I checked the gaps in the distributor and put it back on, the single bore on the crankshaft pulley aligned with the pin marking on the engine block and the grove in the camshaft which you see when you take the oil cap off aligned with the marking there. Since you can put the pulley on the cog in only one way I`d say yes. Also cylinder one (the one nearest to the cam cogs)was at tdc.
I`m also sure I checked that when I put the engine together last year. Is there a way to put everything together and be one camshaft revolution off? I dont think so, but I might be wrong.
Can be a wrongly put together crank- camshaft combo be the reason for this problem? I heard that the engine still runs (badly) when the alignment is off by one tooth.
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boondougal




Joined: 10 Jul 2005
Posts: 520
Location: Shavington (near Crewe)
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1989 Toyota MR2 Mk1b

PostPosted: Tue Nov 21, 2017 8:46 am    Post subject: Reply with quote Reply with quote including images

Check if all cables are plugged in correctly (they werent at first, in fact plus and minus on the coil were swapped)

Surely this can not be good for it!

the other thing that springs to mind is earthing?
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Hasskarre




Joined: 19 Nov 2017
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PostPosted: Tue Nov 21, 2017 11:02 am    Post subject: Reply with quote Reply with quote including images

Probably not, thats why I checked again with a different coil and opened the igniter module to check for damage. But the other coil also didnt work and the igniter looked healthy inside. And the coil still passed the resistance check afterwards.
I guess it never got the signal from the igniter to generate high voltage, since the igniter doesnt get any signals from the ecu (I think).

The engine has three earthing points and when I checked I got earthing on every component. The cable near the coil is also at its earthing Point.
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Hasskarre




Joined: 19 Nov 2017
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PostPosted: Mon Dec 04, 2017 6:30 pm    Post subject: Reply with quote Reply with quote including images

Here`s the list of things I have done since the last post:
Made sure that I have the correct parts numbers for ECU, Igniter and distributor for the VIN of the car. ECU was wrong. It had the end number 17140 in it, the correct ECU is 17170, so I put that in. No spark

Tried with another igniter, another ECU and another distributor from a car with running engine. All matching parts numbers. No spark.

Measured once again if the ECU, igniter and coil get 12V and ground at their respective pins. They do.
Measured once again if all four cables that go from the igniter or ECU to the distributor are connected. They are.

Tried to measure the NE and G+ signal with an oscilloscope to see if I get the signal I expect to see, which I didn`t. Maybe I used the oscilloscope wrongly by using DC instead od AC. I`ll try again tomorrow.

Unfortunately the Workshop manual doesn`t go in depth about the interaction between the ECU and the Igniter, besides which cables go where. Does anybody know of a faq/post/blog/etc. that gives in depth information about that topic?

The closest thing I could find was a picture on megamanual that I cant link due to my too low post count.


By the way, is it okay to post pictures/material from the workshop manual here?
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Hasskarre




Joined: 19 Nov 2017
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PostPosted: Wed Dec 06, 2017 6:06 am    Post subject: Reply with quote Reply with quote including images

Yesterday I tried measuring with the oscilloscope again, this time with AC.
I tried to get a signal readout from the G+/G- circuit. I tried measing each cable aginst ground and both against each other. I got no signal, not even any current.
To check if I was using the device wrongly I went to a simpler method, which was wiring a lamp into the circuit to see if any current goes through it. Upon cranking the lamp didn`t glow one bit. There should be some Kind of current in this circuit for the magnets in the Distributor to work with, right?
I found a wirung diagram of the Vast Distributor System Toyota uses with these engines, which has unstated engine sensors included in the wiring.

Are there any other electrical components that have an influence to the ignition system, that are not shown in the official wiring diagram which might hinder the ecu to send the currents needed for signal generation?
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jimi




Joined: 14 Dec 2004
Posts: 2062
Location: Kingdom of Fife
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1988 Toyota MR2 Mk1b

PostPosted: Sun Dec 10, 2017 10:23 pm    Post subject: Reply with quote Reply with quote including images

Have you used the BGB fault finding procedure ?
Also this document may help you to understand how the system works and also has a fault finding chart
CLICKY 2
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Hasskarre




Joined: 19 Nov 2017
Posts: 7

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PostPosted: Mon Dec 11, 2017 8:19 am    Post subject: Reply with quote Reply with quote including images

Quote:
Have you used the BGB fault finding procedure ?
Also this document may help you to understand how the system works and also has a fault finding chart


Yes, please see my first post for that.
The document Looks very recourceful, thanks for the link. Unfortunately the BGB doesnt go into full depth regarding the inner workings of the ECU and the Igniter. And the fact that there are different kinds of wiring/plugs for the 4age, depending on which market the AW11 was made for doesnt help.
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jimi




Joined: 14 Dec 2004
Posts: 2062
Location: Kingdom of Fife
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1988 Toyota MR2 Mk1b

PostPosted: Mon Dec 11, 2017 8:35 pm    Post subject: Reply with quote Reply with quote including images

Your unlikely to find anything on the inner workings of the ECU, AFAIK Toyota never made that info available.
Have a look at the Toyota 4F/4A-GE engine manual, it has pinouts for different variations of the 4A-GE. you can download it from my web storage with this link CLICKY
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Hasskarre




Joined: 19 Nov 2017
Posts: 7

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PostPosted: Thu Oct 04, 2018 1:01 pm    Post subject: Reply with quote Reply with quote including images

Found the culprit.
I painted the bracket of my igniter and thus it had no earthing.
Engine started with no problems and runs like new.
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