90 740 turbo ezk/ecu issues

I have been having a stalling issue with this for 2 months now there were a few things wrong that I have fixed my problem now is It stalled just died pulled off the road and did some checks fuel pressure is good at 43psi with no bleed down new bosch fuel pump under car and filter as well. OEM new fuel pump in tank new main relay OEM Volvo. relay is not getting hot.

I have spark and fuel no check engine lights has a new ECU 954 well new used as I thought the no injector pulse was due to the 939 ECU that was in the car. obviously, it wasn't the issue or maybe I have a bad ECU again I have t5 injectors with the resistor pack bypassed. the car ran fantastic for 3/4 of a tank after I installed the ECU was hot outside and didn't miss a beat until the temp outside cooled off and died on me that evening. so I had it towed home and pulled the ECU out and ezk out to check the wires between them on poles #1 and #28 on the ECU from the ezk. because everything else is good my ect is reading correctly new etc as well as a throttle switch is new and a cps is new bougicord all of them are testing out ok and both the ezk and ECU see the cps when tested with the diagnostic connector.

the only thing I have found any info on is if the ezk doesn't send the run signal to the ECU on #1 and #28 on the ECU the ECU will not pulse the injectors the noid light is bright with the key on at the injectors no pulse at all when motor is cranked. I have checked both the wires and have no grounds and have continuity.
now my question is according to the shop manuals the 131 code is for #1 not receiving a signal and #28 it does I do not have any codes whatsoever threw all of this. will the ezk send the same signal of 5volts to both poles so if I crank it to check I should see that? it doesn't say in the books for both only pole #1

forgot to mention it has a known working good MAF sensor as well.
edit timing belt is recently replaced and all marks line up correctly.

or am I missing something? in the books it says that if the tests are ok or not its in the wiring and connectors yet those are fine clean no corrosion and are making good contact.
this is the last thing I can think of or even find in the literature to solve my problem.
also does anyone know where on the ecu the injector driver is and if its replaceable/fixable?

edit: the radio suppression relay is also good I have 5 of them.

gah I am scatter brained today
1990 740tic b230 ft LH 2.4 mildly modded IPD turbo cam adjustable boost late 9 series ic and radiator ECU and EZK gold chipped with either TLAO or KL racing or stock chips. everything is set to stock atm trying to solve this issue IE boost and cam timing.

Have you replaced the ignition amplifier (aka power stage or ignitor)? Sometimes when they start to fail, you can still get a spark but it's weak and/or not consistent.

yes I have several working ones. would that stop it from pulsing the injectors?

oh but if the powerstage isn't functioning correctly the ezk won't send the run signal to the ECU then? I am guessing since that part of these is for if there is an accident it will shut off fuel if the engine has died? I will run threw the diagnosis for the powerstage first thing in the morning maybe the wires are bad there they look fine like all the others but they are by the battery so whom knows.

Could the injectors you are using be killing the injector driver circuit?

The car ran for a tank (approx) on the replacement ECU, then died, you said. But you used the same injector setup on the old ECU for quite some time with no issues in that regard?

It certainly sounds like the ECU is the issue, if the ignition side is giving the appropriate signals & you have no inj. pulse. I guess you'll know after you try a repl. power stage.

well I wasn't able to get out of bed today back was killing me so I didn't get to the car today I will have to try in the morning. as far as the injectors those were put on at the same time as the new ECU the stock injectors were falling apart when I pulled the fuel rail pintles were sitting loose in the hole that the injector sits in.

I doubt the injectors are causing the ECU to fail as I checked each one's resistance before I installed them. and the resistor bypass I measured each wire's resistance and checked for continuity before I install it as well.
it is possible they could be doing it they all light the noid light well the connector to each injector lights the noid light with the key on.
the ECU is a 954 the old one was a 939 I imagine the worst case I can repair the injector circuit I have a few friends who are good at electronic repair bah ill think about that after I check the power stages and the wiring tomorrow.

ok so I checked the power stage and pole number 2 key off volt meter said 00.7 ohms now I am not sure if I should interpret that as ok or if I need a new ground wire I went with ok and checked the signal voltage key on pole 4 12.45 volts the book said try another power stage. did that car fired right up. after running for about 15 minutes at idle check engine light came on.

guess what code popped up? yep 1-1-2 fault in ECU.
also had a code 2-3-2 that one is saying it's too rich at idle.

cleared codes and started the car back up ran for 15 minutes no check engine light shut it off checked for codes.
The only one that was there was the 2-3-2.
oh, I also checked the resistance of each injector they were all at 13.4ohms warm engine.

so I'm sure the oil is partially saturated with fuel after trying to start it when it died the other day due to weak spark? I can smell fuel in the oil very faintly its probably enough to set that code.

my biggest concern is I don't trust driving this car any longer can yah blame me lol 10 times Ive had to get it towed home in the last 2 months. I will say this I've gotten my moneys worth out of my car insurances road side assistance I have had to pay but 20 dollars out of all those times.

so the only thing I found off with the power stage is that ground showing 0.7 ohms is that with in tolerance?

Read the No Start in my sig.

ZVOLV said:

Read the No Start in my sig.

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thanks for the replies
Yeah I've done all that except for using a test light I have a noid light to check for injector pulse.
things that have been replaced are
New bosch main fuel pump and a new Volvo OEM in-tank pump all wiring is good for the fuel pumps as well as a new main relay.
I have 43psi fuel pressure
new borgicourd cps
new maf
new throttle switch new cap and rotor and plugs the coil is with in specs according to the Volvo shop manual
new\used ecu had a 939 in it now has a 954
new bosch power stage.
t5 injectors in good condition with the resistor pack bypassed they are reading 13ohms.
timing belt was done with in 5k miles and its all lined up still
new crank pulley so its not slipping.
new ipd turbo cam about 6k miles ago all tolerances

had spark but it obviously was weak due to power stage I am only questioning the ground for it because in the Volvo shop manual it says it should read 0ohms and I am getting 0.7ohms my problem has been intermittent and never has set a code until today
the bad ECU code not sure why that would be there on a freshly installed ECU that didn't have one when it died last time.

the car is running now I am just not sure if I can trust it as per that ground wire resistance ill probably just make a new ground wire if it dies again. and change the oil lol
thanks for the help everyone hopefully this problem is gone for good.

A voltage drop test is the proper method to check connections and wiring.

The 954 ECU that I sent you came from the running car and I had it in my own '93T for about 400 miles to see if there was any difference from the 939 as far as CO readings, gas consumption or anything else (no difference registered). Anything is possible but it's just not very likely that 2 different ECU's are causing same issue if I am reading your post correctly.
How is the wiring to the radio suppression relay? Any green colored corrosion inside the plug?

PCH said:

The 954 ECU that I sent you came from the running car and I had it in my own '93T for about 400 miles to see if there was any difference from the 939 as far as CO readings, gas consumption or anything else (no difference registered). Anything is possible but it's just not very likely that 2 different ECU's are causing same issue if I am reading your post correctly.
How is the wiring to the radio suppression relay? Any green colored corrosion inside the plug?

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that bad ECU code happened only once and it has not reoccured. the radio suppression relay is new and the connector is clean with no corrosion.
the car appears to be fixed after I cleared the codes changed the oil and reset the fuel trim all is good no rich at idle code and she starts and runs very smoothly. and as far as MPG I've gained 2 MPG with the new ECU and t5 injectors. everything I have replaced had some form of issue which isn't surprising since it's all 30+ years old and has over 200k miles on it so it was due it's just funny how it all went one right after the other. but sometimes when you replace one piece of a machine the other parts show their wear even more and will break since they are the weak link now.

there is no problem with the ECU I bought from you.

what is nice is even on a hot day yesterday driving around none of the relays even got remotely hot just slightly warm. which is a big change considering the main relay got so hot that you couldn't touch it.
This car's wiring is in superb shape for it being as old as it is. hell the car doesn't look like its 30 years old paint is almost perfect still interior has some fading on parts of the dash it was a Cali car.

you know what I really need is the Volvo ST tool that thing would make diagnosing anything with this car a very quick and easy process. I wish I could find one for sale no one I've approached even knows what it is.

Please tell me what the Volvo ST tool is?

I know of VADIS, VIDA. The old models used a magnetic sensor and had a special tool to interface with the connector on the top of the valve cover. I think that was the Volvo Monotester or something like that.

dl242gt said:

Please tell me what the Volvo ST tool is?

I know of VADIS, VIDA. The old models used a magnetic sensor and had a special tool to interface with the connector on the top of the valve cover. I think that was the Volvo Monotester or something like that.

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it is listed in the manuals as the tool to use to diagnose electrical issues with the ezk and ECU
it has several functions one part is you hook it up between both ezk and ECU plugs and it has an adapter that has all the pins out for both numbered then you follow the book as per testing each pin. it also has a code reader adapter as well this tool would make diagnosing any electrical issue a breeze since you can sit in one place and test each circuit not having to go and unplug this and that and check it allows you to check it right in your hand. I have some friends in sweden and they asked around for it as well no one has it or knows where to buy it.

Thank you. I had no idea they supplied this back then. No one will have such a useful tool nowadays. The dealers probably dumped them all in the scrapyard when it came time to update from working on LH injection.

In my job we used to make or buy such things. They were called breakout boxes. The unit connects between the device and the cables to it. They let you test all the signals and verify continuity. The ones for DB 25 connectors had leds for signal testing. Those were the good old days of my profession. Good times.

dl242gt said:

Thank you. I had no idea they supplied this back then. No one will have such a useful tool nowadays. The dealers probably dumped them all in the scrapyard when it came time to update from working on LH injection.

In my job we used to make or buy such things. They were called breakout boxes. The unit connects between the device and the cables to it. They let you test all the signals and verify continuity. The ones for DB 25 connectors had leds for signal testing. Those were the good old days of my profession. Good times.

Click to expand...

yes and that tool would actually make the LH system easy to diagnose and keep using. you are right in that they all dumped them I've asked friends in Sweden and Germany if they could possibly find one and no luck there. I was thinking about fabbing one together but to be honest ill probably just end up going Mega-squirt or Maxx-ECU and remove all the LH ECU EZK and go with a map sensor and coil over the plug to eliminate the MAFF and distributor and also go with a throttle position sensor vs throttle switch. and have one ECU with software to set my own tunes up and have datalogging ability. so many positives to getting standalone that would eliminate many headaches.
yes, the breakout boxes I remember those we had for the sun microsystem scopes for hooking cars to the scope back in the day when tune-up shops were a big thing. I was a manager/ technician for a precision tune for a few years I keep threatening to buy myself a nice oscilloscope those are great for checking the entire spark process for engines.
that made diagnosing spark issues a breeze if the pattern deviated in any way on one you knew right where the problem was.

I ended up buying a surplus scope from a college. It's a Leader probably 25 years old but only cost me about $160 plus shipping.

Stand alone is the way to go. We have a large and experienced group of people here and I feel the pull of changing my old obsolete kjet to efi. Just not ready for the expense yet.