This was in my first 940 Regina running problem, and I don't recall seeing the cause turn up before, in nearly 6 years of almost daily scanning here .

Symptom: Abrupt power loss at 50-60 mph, after about 3 miles. No problems in preceding week (175 miles) on local gas fill up.

Indications:

1) Tach did not fall to zero, but dropped slowly as I pulled over to shut it off and swap in a good Fuel relay. Engine then restarted normally.

2) Engine failed again in about a mile, restarting quickly. This repeated two or three more times on the remaining 3+ miles to the store.

3) After a few minutes of shopping, the engine started normally and was trouble free on the 7 mile drive home.

• Next was a two day interval of no driving (waiting for salt-free roads). At that time, the plugs looked clean and normal, and I rigged an ammeter in the Fuel Pump circuit.

4) Installed a new RS Relay (FCP Hungarian) and started out on the same route. Got the same power loss symptom in less than 1/4 mile. Tach was normal as before, and Fuel pump current was a steady 8 Amps.

5) Also found that it would restart "on the fly" by turning the Key Off and On again.

6) After about 3 miles and several "on the fly" restarts, the trouble went away. And as before, the trip home was trouble-free.

An under-hood repair solved the problem, and confirmed my hunch that the plugs would have been "clean and dry" if checked. (I didn't get to them on the road.)

Any guesses as to the culprit?


--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

I have been reading this thread with interest because my daughter's car ('91 Regina 740 275K)showed some similar symptoms recently. Intermittant power loss. Inability to climb hills. I cleaned the flame trap, that was plugged. That seemed to help- then it happened to me. I now wonder about a test for a plugged converter, because back pressure in the exhaust really showed up after a new aftermarket header pipe to pass inspection. I've been driving it with a plug out- not really a long term fix.Fuel filter is good.

Bruce, you know you're supposed to start buying all sorts of expensive parts and replacing them until it runs right - just like a lot of the "professionals" do (which of course would have never happen in your case). Maybe when you replaced the battery you would have bumped the ground block and it would have fixed it.

I am going to guess it was the coolant temp sensor and/or the connectors for it (or a coolant air bubble). My main reason for the guess is the timing - at 3 mi, car will not be cold, but probably not warm at this time of year. By 6 miles, it should be at operating temp most everywhere.
--
1990 740 Turbo, on its way to stock specs, maybe beyond

Hey Bruce,



Was it a dirty ground at the front fender ground point? No one seemed to mention the impulse sensor... I don't think Regina has the same telltale movement of the tach (dropping to zero) as the Bosch setup does. Anyhow, glad you found the problem. I'd like to know, as my '92 740 has Regina as well. Like mentioned before, I bet its simple, but overlooked.

"Age and treachery will overcome youth and skill"

Cheers,


Jon 'Uncle Olaf'

"Was it a dirty ground at the front fender ground point?"
• Right you are, Jon. The one on the right side. I suspect that battery fumes had their effect over several years, but haven't yet looked at the left side ground to compare the two.

"No one seemed to mention the impulse sensor... I don't think Regina has the same telltale movement of the tach (dropping to zero) as the Bosch setup does."
• The Tach is driven from the Rex ignition's version of the EZK Power Stage, meaning the basic ICU (driven by the CPS/impulse sender) was working.

"Anyhow, glad you found the problem. I'd like to know, as my '92 740 has Regina as well. Like mentioned before, I bet its simple, but overlooked."
• I think most people don't realize how similar the Rex/Regina is to the Bosch EZK/LH 2.4. Same functions, just different components. The 940 greenbook diagrams show both versions, making the comparisons fairly easy.

This stall-out came down to process of elimination:
1) Steady Fuel pump current said the FI was getting "go ahead" pulses from a working ICU.
2) The tach also confirmed the Ignition and Power Stage (but not coil-dist-wires-plugs)
3) Had the Coil, etc. been the cause, I would have expected some sign of fuel soaking when I looked at them between test runs, but they were a nice tan-white with no sooting.
4) That left the Injectors (voltage supply), from the well-known Radio (noise) Suppression Relay/RSR. (An item the 240's are [luckily] missing)
5) A new RSR didn't change anything, and the power to the RSR coil (From FI System relay 87/1) was also common to the Fuel Pump Relay coil and the ECU. Any of those failing would rule out the steady pump current in #1 above.
6) So I went for the RSR relay ground, which looked cruddy but was apparently making an intermittent (and maybe under-hood ambient temp-related) connection that allowed some OK running when warmed up — as on the two good 7-mile runs home from the store.


--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

good catch. i had the same problem with an 87 740t that would stall when the high beams were engaged. high beams meant too much amperage from the poor ground and kill the rs relay. i'll have to watch for the fluttering tach on stall with regina cars. thanks, chuck.

Hey Bruce,


From the hints you gave, I thought it was something electrical and underhood. You are right about the tach, it does get its signal in the same manner as in the Bosch equipped cars. I was thinking about something I read that the tach doesn't seem to quiver upon cranking in the Regina cars. Anyhow, I'm glad you found the culprit, and the game was fun. Thanks for sharing your finding.


Cheers, Jon 'Uncle Olaf'

Hello Bruce:

How about a bad ignition switch? Do you have a large ring of keys?

Cheers!

Hello
i guess it was a small problem.
i dont much like guessing much.
good to hear its fixed.
Mike

Hi Bruce.
i didnt want to spoil the fun.
i have read and saved that e-mail.
i will tighten/clean the same contacts on my cars probably this weekend.
thanks
Mike

Fouled fuel filter?
(Clue = ..clean and DRY)
--
George Downs, Bartlesville, Heart of the USA!

Bad/loose ground somewhere in the ignition circuit?

Lucid,

I'll take a guess at a weak air intake snorkel collapsing under vacuum. Or, maybe it was a fuel pressure regulator?

If making two guesses is cheating, I'll go with the first one.

Charley

Hi Shannon,

You were so close. I thought the game would soon be up when the word "ground" appeared.

Admittedly my luck was enhanced by the luxuries of time and a warm (well 55°) garage.
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.