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Mystery Regina Project


New member
Feb 13, 2023
Knoxville, TN
1990 Volvo 740 2.3 N/A Auto 4spd that's at 205k miles with Regina-Rex.

To start things off this car has come to me in a unique condition, it "died" while driving and the harmonic balancer was found to have fallen off. When I acquired the car the harmonic balancer had been "put" back on but was told the car makes a very "bad" sound when the engine turns over. It had sit for 2 months at this point.

The first thing I did was I pulled off the harmonic balancer and found that the crank sprocket key had broken so it would not turn the timing belt, thus no cam movement. I replaced the cam sprocket with a spare good one and put the engine back in time and a new chuck key for the harmonic balancer. After assembling everything back together and bumping the starter I was getting a bad grinding sound and the engine was hard to turn over. I decided to pull out the compression tester and check compression to see if something may have went in the bottom end. ALL 4 cylinders came back at 160psi, +-4psi. I made the decision to pull the engine since I had no next guesses as to what was making the grinding noise except for maybe main bearings.

Upon seperating the engine from the transmission and raising it out of the car I found the culprit for the grinding noise. The flywheels bolts had all backed out about half their length (one head was sheared off completely) and the flywheel was freely moving around. Upon this finding I decided that whoever had worked on this last may have not done the due diligence to make sure everything was torqued to spec. I found several oil pan bolts as well as the back crank plate loose as well. The main caps, rod caps, and head bolts were all in spec (LUCKILY). The flywheel bolts were in rough shape thread wise due to being driven (who knows how long) in that condition so I switched them out with another good used set I had and applied loctite and torqued them all to spec. NOTE for later: I noticed that there were 4 numbers etched on the flywheel (1,3,5,8) there was the same done on the crank. I made the assumption that this was the correct order that the flywheel was to be put on for the crank sensor timing marks.

Reinstallation of engine and replacement of a few seals went by smoothly and then began the troubleshooting to actually get it to run. So for first, the grinding noise and engine drag was gone after having the flywheel fixed. Then there was a no start, upon turning the key to on there was a momentary fuel pump prime and the first click from the fuel relay was present. I then tested with a noid light and multimeter at the injector connectors, there was ground pulse from the ecu present but no 12v power which was found to be a bad RSR (original '91!). Replaced that and with the fuel rail not mounted (but grounds bolted in) I confirmed all 4 injectors were firing. After installation of the rail it was definitely hitting but inconsistent, rpm gauge was bouncing so cps was working. I had replaced the spark plugs with NGK BPR6ES gapped at 0.7,mm. But I found the spark weak at the wires (they were old and one of them actually broke when disconnected from the plug). Before going to buy new wires I went ahead and pulled off the distirbutor cap and found some varnish in the cap as well as some small black (plastic pieces?) laying inside. The cap was cleaned out and I purchased a new Bosch rotor (the current one was cracked at the plastic base and loose). Out of curiousity I tested the spark from the coil with the 'ol insulated screwdriver and found the spark to be a weak orange small zap so with all this info I went out and got a new rotor, wires, and coil. After replacing all these I had a strong blue spark at all the plug wires when turned over.

And with this we finally got to our first startup, or somewhat. Upon starting up the idle was low and it eventually stalled after 10 seconds. After a few repeated tries it eventually would only "idle" at 700rpm with the throttle all the way open and it would run like this as long as it was held down. The first thing from here was I checked fuel pressure just to confirm pump and fpr were functioning correctly, got a 48 psi of fuel pressure almost instantly upon first key turn to on. I rechecked the compression just to make sure timing belt was still on and I had the repeatable 160psi across all 4 cylinders so for now I'm taking a break for the moment to write these findings down here, as this is an extra extra car there is no priority to have it fixed.

So in summary as follows:
New NGK BPR6ES Plugs
New Plug wire set
New Rotor
Good Cap
160psi across all 4 cylinders
Strong spark at plug wire ends
New RSR relay
48 psi at fuel rail
Injectors pulsing

Only barely idles with throttle all the way open

Random things:
-Sprayed the whole intake with starting fluid to see if I missed a vacuum line / or a leak, (no change).
-Rechecked all engine harness connectors and pin conditions.
-Cleaned engine grounds and fuel rail grounds
-Disconnected Cold start injector to see if any difference.
-Obd code check gives no codes.
-All fuses checked out good, however Fuse #12 consistently blows when key is turned on
-Car has no cat installed.
-Fuel at rail seems to be good, no rust or weird appearance.
-For fun I tried a good known FI relay as well as a new CPS (from another car).
-Ecu is a junkyard pull unit.

Being the first Regina/Rex car I've worked on, I don't have much knowledge on if the ICM or ECUs go bad? I doubt so but just a question I thought I'd throw out. I'll be checking for any input every now and then. Thanks!
It seems to me that it's time to verify both the flywheel timing and the timing belt alignment. I don't know how to verify Regina flywheel timing but there is probably a procedure in a green book. I would check on ozvolvo.org for a green book that may help you.
Have you checked ignition timing? I think it's fixed on Regina like 2.4, but it can't hurt to see what it's doing.
Finally got around to rolling this one back into the shop and after pulling the transmission this is what I have with it set at TDC.

This is a new crank pulley and mark has been verified correct.

That yellow arrow is pointing a funny direction :-)

The following is taken from page 24 of the Volvo service manual section 2 (28) Ignition systems 700 1982- which can be found on the net as a pdf by searching "Volvo TP 31397-1 Ignition-OCR"

The section is a little confusing because based on the flywheel orientation it looks to be correct when compared to the diagram from the handbook with the image of the crank sensor, however that is wrong. The location of "TOC" (equivalent of TDC) is actually where the crank sensor also resides and when reading the last sentence from the A. block it states "The control unit identifies TDC as the point 90° after the passage of a long tooth".

So the yellow arrow that can be seen in the third image from my set of photos needs to be pointed at the crank sensor. I've attached a non confusing version for future referencing. Looking forward to any thoughts from what I've gathered.

Corrected Bendix Regina Rex flywheel timing mark configuration diagram
I doubt it. If #1 TDC were identified electrically simultaneous with its occurrence, how would Rex have time to build in advance? Maybe we are both saying the same thing?
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I've attached a non confusing version for future referencing. Looking forward to any thoughts from what I've gathered.
Technically, you're right, the arrow needs to point up (when at actual TDC).
Technically, the manual is right, since the section is called "Design and Function", not "How to Install".

I don't know where your painted arrow came from. Previous guy who left everything loose after he took it all apart and put it back together after it "died", because he had no idea what he was doing?

Either way, I prefer using Repair manuals, rather than Design and Function manuals for most things.
I've added a pic from one of them.

Also, a reply post on Matthew's Volvo site says :
"you want to install flywheel with the two rivet looking pins at 3 to 3:30."
Your photo shows them at the bottom, instead of on the right side.

Update, it runs after turning the plate 90° counterclockwise, lining up yellow arrow with crank sensor.

More photosss

Confirmed printed arrow does indeed line up with the front marked yellow arrow.


Where the blanks end up