I have a 1986 740 gle wagon I can not get to start at all. No spark, no fuel, New harness under the hood changed that issue along with new ignitor and ig coil. I've decided at this point since the shop it's at has taken 5 months to work on it to just switch the guts out with a known working volvo. My doner car is a 1984 240 DL.

How much interchanges off the bat with the 240 and 740? Computers have the same connectors but different amounts of pins, injectors, air flow sensor, and stuff under the steering column look identicle. Has any one else mixed and match these two models before and what was your experience?

 

the 740 has a *completely* different wiring harness, both interior and engine. inside, the 740 fuse and relays are on a central panel ont he transmission hump behind the ashtray, while the 240 fuse panel is on the far left lower A pillar, and the relays are scattered randomly behind the dash.

the 86 740 is probably Bosch LH 2.2 injection, and Bosch EZK-117k ignition

the 1984 240 is probably Bosch LH 2.0 injection, and a Chrysler ignition computer (don't ask, don't tell). completely different wiring harnesses for this, too.

the 740 has a distributor on the back end of the overhad camshaft, while the 240 has the distributor on the side of the block, run from the intermediate shaft.

the radiators are different. transmissions are basically the same, drive shafts are different lengths, drive shaft carrier bearing assemblies are different, front and rear control arms are different, rear axle is the same type axle but have different welded-on mounts for the thrust arms, for the trailing arms. the actual engine blocks are pretty much the same, except for the distributors,


it should be much easier to debug whats wrong with the 740 than to try and swap motors and electronic bits. an 85-88 740 would be about the same as your 86, or at least the changes would be much smaller and adaptable (same ICU, same ECU, same yada yada). 89+ gets into LH2.4 and EZK-116 and CPS instead of Hall sensor timing and....

 

I had seen major harness differences when I first inspected an 88 240 to compare. It looked 40 percent different. Wiring colors as well. I don't have to use my main harness off my 740 at all if I don't want to assuming 240s did not have the wiring issues from the mid 80s. I had the option of switching EVRRYTHING outright for about 50 dollars. Other than the Chrysler icm and different ecu what other parts are distinct? Are the relays different outright or just the same ones in different locations? I seen the 240s fuses on the left and their housing and liked that set up better anyway along with it's location.
Other than matching components to their New wiring what other issues do you face when doing this type of swap . steering column wires also look identicle for the most part.

 

completely different electrics behind the dash, which is where the 740 ECU and ICU are located as well as the majority of the vehicle relays.

seriously. don't even think of this swap as the solution to why your car isn't running, unless your engine is mechanically broken (highly unlikely).

only wires on the steering column is the horn and airbag, unless you mean the turn signal and wiper stalks. those are different between 740 and 240, too.

both 240 and 740 have bad wiring insulation from about 1982 to mid 1987.

 

Lets switch it up then. How about replacing the insides of this 86 with the wires from a 1889 740 but with the Regina set up. How much of a match would that be ans would I absolutely need to bring the ecm out of the Regina along for the ride with this switch or would a computer from the older 740 still mesh with the wiring with the Regina harnesses as lon

 

regina works totally differently than LH.

with LH, the primary input to the fuel injection is a mass airflow meter (MAF, aka AMM), this tells the LH computer how much air the engine is ingesting.

with Regina, there is instead a MAP, Manifold Air Pressure meter, they use this, plus throttle position, plus RPM, plus air temperature to calculate how much air the engine is ingesting, so they know how much fuel to squirt.

plus, the injectors are different, everything really. so you'd need to switch the whole air path, fuel path, AND the computer, along with the wiring harness. oh, and Regina cars use REX ignition, which has a different ICU and uses a completely different coil. so you'd need to swap that in too.

 

btw, no spark AND no fuel, I'd start at the hall sensor in your distributor, and verify THATS working, without that, you won't get fuel injection or spark.

 

Well I already bypassed the dizzy too and no spark from the coil. I know my fuse box has melted outter areas which always had me puzzled due to the areas closest to the fuses not being melted. The relay that controls the head lights has a melted housing and I replaced that and there was another fuse I seen melting its housing a bit so we are focusing on the whole fuse box. Since you know the Regina so well tell me with the Bosch set up on this 85 what is the bare minimum of those wires, sensors, and relays I need for the car to start properly? I'd much rather do it like that then from there manually add back other systems in the car. From there I'd just give new wires and fuses and relays to those items that I know is new. How much can be missing before the ecm gets irratated with me?

 

the hall sensor in the distributor provides the master timing for the whole system, much like breaker points did on old school ignition systems. if its not working, the ICU won't tell the coil to spark, and the ECU won't tell the injectors to squirt fuel.

catch-22, I don't have any wiring diagrams for 740's prior to 1991, and those use a different EFI than an 86.

I suggest going down this troubleshooting list. https://www.volvoclub.org.uk/faq/Eng...eSymptoms.html


btw. I don't know Regina at all well, I've never seen one in person.

LH2.2 at a minimum requires A) hall sensor timing pulses (sent to ICU, and forwarded to ECU), B) power module for spark. C) coolant temp sensor, D) MAF/AMM for airflow (althought it will run poorly in 'limp home' mode with the MAF/AMM unplugged). and E) fuel pump and fuel pressure regulator to provide proper fuel pressure.

 

Well since Regina isn't really isn't a good thing to mix and match with this Bosch system I guess the question now is which fuses and relays do you believe I should leave remaining with the new bare bones no frills set up I am going to have to use with this 1986 740? And by power module you mean the coil?what needs to still be left connected to the ignition switch too?

 

re: fuses and relays, there are hardly any fuses or relays involved with engine operation, other than A) the main fuel injection and fuel pump relay thats behind the ashtray, B) the 'radio suppression relay thats in the engine compartment, and C) the main ECU power fuse. all of these must be operating for the engine to run, however, none of them are involved with ignition/spark, so if you don't have spark, they aren't your problem.


the actual ignition control unit (ICU) is behind the dashboard, its output goes to a power module thats a 5 pin device on the left fender, its the power module actually drives the coil.

a good test would be to hook a test light up to the input to the power module and crank the engine, if that input blinks, then hook the test light up to ignition coil pin 1, and crank the engine, if the light doesn't blink then your power module is bad.

as I said, I don't have 740 wiring diagrams handy so I can't be of more specific help here. this is all basic automotive electrical troubleshooting stuff however. ok, wait, here's the greenbook for a 1987 740, whihc should be pretty much the same as your 86. http://www.volvowiringdiagrams.com/v...20Diagrams.pdf

go to page 34/127 (labeled page 32), thats the EZ 117k Ignition System for B230F/FT. part '419' is this power module, while part '260' is the ICU. Power module input is pin 5, power module output is pin 1, which is connected to coil pin 1. the following page shows where all the parts are located.

 

here's another good troubleshooting procedure, since you chose to ignore my first more involved one.

Electrical-Ignition

 

Okay after lookin at all those links on a desk top i seen lots of data on some issues and lots of vagueness on others.

This is what im gonna do, run a switch in place of the old ignition switch to the dizzy's hall effect sensor then a new wire to the ecm pin for that then a wire to the fuel pump from the ecm fp pin then a wire fromrthose sensors to the ecm pins corresponding to them and with fuses then a switch to the main relay when i figure outvwhich pins do what on it then that's it. I dont think mine has the noise reducer relay. Are those components enough for start?

 

ugh. no no no. the hall effect sensor in the distributor puts out a very low level signal that is NOT connected to ignition power, rather, its amplified by the ignition control unit, which uses it as the timing base, and calculates the spark advance/retard based on a lot of parameters, and sends a signal to fire the power module at the correct time.

all 740's except the very first year have the 'radio suppression relay', it provides the power to the fuel injectors (and has nothing to do with the radio, the name is confusing).

virtually every circuit on the engine, ECU, and ICU, is required for proper engine operation, you can't just hack it up like a 3rd grade electric project. follow the wiring diagrams, determine what circuits aren't behaving properly, and diagnose why, IF its bad wiring then rewire the harness.

 

You gave me the minimum the car needs to run and i was trying to ax every last thing that wasn't on thw short list you gave so are u or are u not sayin i can have a bare bones set up?

 

Your sending me mixed messages here

 

Sounds like the message here is to fix what you have.

 

that.