LocostUSA.com

Hello Everybody,
My first post.....
My project is powered by a Toyota 4A-GE engine, blueprinted and mildly massaged, using OEM induction/injection with superfluous components deleted.
Specifics:
1. DIY Autotune kit built MSII with version 3.0 board
2. Direct Coil control with wasted spark ignition with double-decker modification to circuit board with two BIP373 coil drivers
3. Hall sensor and 36-1 toothed wheel on crank pulley for timing
4. Independent Baro sensor mounted to circuit board
5. FIDL controls TVIS, opens secondary runners above 4500 RPM
6. IAC1 controls electric radiator fan, turning on at 200 F and off at 180.
7. Firmware version 3.4.1, updated this AM.
8. Tuner Studio MS v. 2.6.14.
9. DIY Autotune Relay Board interfacing ECU to sensors/engine components.
10. Fuel pump and coils ganged to same relay/screw terminal on relay board.
11. Scratch built whole vehicle wiring harness.
Most of the summer was short test runs while I did battle with the Colorado Department of Revenue on getting an assigned VIN, license tags, etc., but it started and ran pretty well except for some rough running at steady state highway speeds.
Registration, License plates, insurance finally came through in early September.
Sometime during the Fall, the fuel pump control started malfunctioning. Specifically, it's supposed to run the pump for 2 seconds when the ignition is turned on, but then turn off until cranking is detected, whereupon it starts up again to supply fuel for starting and running. At some point, it started running the pump continuously whenever the ignition is on.
This isn't a big problem except for a couple of situations I can think of.
1. Mishap/fuel leak and engine fire.
2. Burning out coils if ignition left on too long.
DIY Autotune Tech support suggested reloading/updating the firmware, which didn't fix it.
Their suggestion #2 was that it was a transistor problem that could be isolated by disconnecting a diode and referred me to the schematic and/or assembly instructions.
Unfortunately, I can't figure out which component is which from the schematic, and the instructions aren't specific enough to identify which transistor or diode to attack.
Any assistance would be appreciated.

In a "normal" installation, the fuel pump should be powered by a relay in your wiring somewhere. It should be powered from the ignition switch and switched on/off by the other side of the coil. I would start there. If that is not clicking off after 2 seconds, check the voltage on the coil side going to the MS. That should see 0V for ~ 2seconds after ignition is turned on, then go back up to 12V. If this sees 0V continuously then there is either a) a wiring short somewhere or 2 something inside the MS board.

If you hear the relay cycling, but the fuel pump doesn't shut off, then you might have a short in the power side wiring to the relay.

Do you have a JimStim? This would be easy to verify if the problem is within the MS board or not without having to disassemble the unit.

If you have identified that the MS unit is faulty, the fuel pump control of the relay is switched by Q2. Q2 is driven by Q19, so that might also be the issue, probably not. D4 being shorted could also cause the relay to be on all the time.

Hope this helps.

_________________
Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766

I forgot to mention that the JimStim behaves the same as the fuel pump. When it's connected to the ECU, the FP LED turns on when the stimulator is energized and stays on as long as there's power to the stimulator. Insofar as I can recollect from using the stim as I assembled and tested my CPU a year or so ago, it would turn on for the specified 2 seconds, turn off, and turn on again when the RPM pots were adjusted to generate detectable RPM.
I suspect the problem is a switching component that has gone south. In which case, one of the transistors may be the culprit. I'm reluctant to start desoldering components on my meticulously assembled board without verifying that they're faulty.
Are there any reliable ways to check components other than swapping them out?

That is how it works.....unless you set the priming pulse to zero.

You can narrow down the culprit without desoldering if you have a voltmeter. Check voltage between pin 33 on the MSII daughter card and ground. It should be low, go to 5V for 2 seconds, then go low when 1st powered on. Make sure your RPM pot is turned off during that test. If that works, then the daughter card/firmware is doing what it should.

Then you cut one lead of D4 and test only using the JimStim. If the FP LED then flashes then goes off, the problem is a shorted diode D4. Replace it. If the FP LED stays on, leave the D4 lead cut for now. Remove the JimStim. mearue the resistance between terminals 1 and 3 on Q2 (emitter and collector). If it is low, say less than 10 ohms, Q2 is shorted and must be replaced. Don't forget to reconnect (resolder) the lead of D4 before closing up the box. It is there for protection of Q2.

_________________
Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766

If that is the only issue with your efi system, you may want to control the fuel pump relay separately.

It isn’t necessary to control the pump relay with the computer, and has not always been the case with oem efi.

For use with standard 4/5 pin relays, I suggest using two; one controlled by the starter solenoid during cranking that falls out when you release the key to the “run” position (positive control) and a second controlled by an oil pressure switch or vaf (negative control) that falls out when the pressure/airflow drops because the ignition has been cut off. The output of both relays is spliced to the pump feed through an inertial safety switch that shuts off power to the pump if the car is hit hard enough and is reset with a button. Orientation of the inertia switch in the chassis and access to reset is important.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Look at page 170 of the MS2 hardware manual. It has the schematic of the fuel pump circuit.
This should better explain the interaction between the components.

_________________
Parts left out cost nothing and cause no problems!!

I cannot recommend bypassing fuel pump control.
Repair it to work correctly, there is really good reason for the control circuit.

Solder bridge on Q2?

_________________
Honey anyone?

Do you mean as apposed to controlling it separately?
If so, what is the really good reason?

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

FIXED!!!!
Thanks everybody, especially Chuck.
I sharpened my voltmeter probes so they wouldn't slop over on adjacent contact points and went through the diagnostic procedure suggested.
Pin 33 on the MSII daughterboard socket worked as specified.
Disconnecting D4 restored normal function to the JimStim FP LED.
The resistance between the outer pins on Q2 exceed my ohmmeter's capacity to measure it.
I'm happy it turned out to be the diode, as it was a whole lot easier to unsolder two diode leads separately than it would have been to do it with 3 leetle bittie pins on the transistor, especially on a crowded circuit board.
Fortunately, the local TV repair shop stocks a reasonable inventory of electronic components and had a comparable diode in stock, even out here in the boonies, so I could replace the faulty one right away.
I, the JimStim, and the fuel pump are much happier now, and the Megasquirt's off the bench and back in the car.
I'd be out on a test drive except it's 15 degrees outside and snowing - not ideal Locost weather.
Thanks again.
John

Congratulations on your troubleshooting and repair skills. Hopefully it won't occur again. If it does, you could add a reverse biased diode across the relay coil. I wouldn't worry about it unless it occurs again. The good thing it is fails in a "drive-home" condition.

_________________
Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766