1991 740 2WD non turbo.
Fuel pumps won't come on when I turn the ignition to the start position. I've pulled the relay and fuse block out to check the fuel relay. All fuses test good continuity underneath the fuse block ruling that out.
I removed the pump relay cover and determined that the contacts are not stuck, are clean and the relay coils are good.
With the relay cover off I can press the pump contact closed to run the pumps to start and run the engine.
The pump relay appears to send the Normally Off position somewhere. I'm assuming that it is to a high fuel pressure control that cycles the pump on/off while driving.
I don't have the electrical schemes for this car, so am quite hindered

I went through the same thing. I messed with the FI relay for the longest time.
Out of the car it looked to be perfect. In the car it took a matchbook shim make it run well.

I picked up a relay from the salvage yard and it's fixed.
I think there might be a diminished electro magnet (coil) in mine.
Just get the relay.

As for the Regina/Bosch debate, I have no Idea, I don't even think that is what you wanted to know.

"Fuel pumps won't come on when I turn the ignition to the start position."

How about when you just turn the key to ON (position II)? I ask because that might be relevant here.

There are actually TWO relays inside the white case. The System relay should be heard and felt to click when the key is first turned on. The System relay powers most everything FI and the pump relay coil (+ side). The pump should be heard to run for a second or so when the ECU grounds the other side of the coil.

Let us know if the System relay clicks at KP II, and whether or not the pump cycles on then off at that time.

BTW, I assume this is a non-turbo car and thus has Regina FI like my '93.
I have the Greenbook, which has the diagrams for both FI systems.

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

Bruce, are you implying that the non-turbo 740s in the 1990 to 1992 range are likely to have Regina injection systems? I'm in the market for a 1990 to 1992 745 right now, and from what I have heard, would like to avoid a Regina system. Also, since my '91 745t is a Bosch, it makes life easier if both cars are as close to identical as possible. If non-turbos are Regina, then will limit my search to turbos only.

Thanks
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Scott Cook - 1991 745T, 1986 Toyota Tercel (Don't laugh, it is reliable, faithful AND gets 41 mpg!)

"...and from what I have heard, would like to avoid a Regina system."

What have you heard, Scott? I've been driving my '93 940 with Regina FI for almost 7 years now and have absolutely no complaints with either the FI system nor the Rex Ignition. In those 7 years I've monitored the BB here almost daily, and can't recall anything to support the negative scuttlebutt that seems more like prejudice ("they ain't like us") or fear of the "unknown". Just because it's not Bosch doesn't mean it's to be avoided.

But the Regina does avoid AMM problems — meeting all B230F (na) operating specs with an inexpensive intake air temp sensor and MAP (Manifold Absolute Pressure) sensor, a GM type costing about $30. The Fuel relay is the same as with Bosch, as are most all the other ancillaries.

The one exception that comes to mind is the IAC valve, and that might swap if the 3-pin plugs matched (regina uses pins 1&3 , bosch 1&2). And the single in-tank pump may not live as long as the Bosch main pump. My son's 92 940 pump gave up at 210K.

But if you're dead set against Regina, I think it began with the '89 740 and continued thru the '93 940.

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

Thanks for the reply Bruce. You have changed my view of the Regina systems, I think. Do they use the same computers that the Bosch systems use? That would be the ones with the fuel pump control circuits that are somewhat failure-prone in certain models.

I'm certainly not going to let Regina or Bosch be a deciding factor when looking for a second 745 now.
--
Scott Cook - 1991 745T, 1986 Toyota Tercel (Don't laugh, it is reliable, faithful AND gets 41 mpg!)

I've been going crazy trying to get my '89 740 GL to start. I replaced the in-tank pump,
radio suppress. relay, fuel pump relay and checked everything. No Luck It cranks but won't fire up. I found a posting on an obscure forum. I can't remember which.
But It worked!.
The vehicle has a regina system. This fellow was at his wit's end also.
What he did: was to remove the coil and clean the two post inside and the spring clips which they fit into with some fine sand paper. Bingo! his car started as did mine. I went one step further and sanded off the areas where the coil joints to the bracket in order to make a solid ground.
I noticed in my diagnosis the spark I was getting was not a brillent blue, instead a weak yellow.
My theroy is the bad connection would't allow enough currnt to power up the injection.
The funny thing, there were no severe signs of corrossion.
$100.00 later and 20 hours of brain drain it was fixed for .50 of sand paper.

Do they use the same computers that the Bosch systems use? That would be the ones with the fuel pump control circuits that are somewhat failure-prone in certain models.

No, the Regina ECU is made by Bendix-Siemans, France. I haven't see a definative ECU problem reported here yet. Hardknocks (mike) says his mechanic knew of some problems that were fixed by the dealer "reflashing" the ECU memory.
(I don't think that's possible with Bosch.)

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

I tried to email you a msg, but it failed,I have questions,you can answer, by your postings obviously, if you would, Please email me@Silverblue58vette@yahoo.com or call me SDHeideckerMBA@612-387-8174 THANKS IN ADVANCE SD

The fuel injection computer sends an "on" signal to the pump relay for about 1 second when you turn the key to the start position. The purpose is to pressurize the fuel system so that the engine can have enough fuel to start. After the engine starts the computer receives signals from the crankshaft position/rotation sensor that tell it the engine is running, and then turns the relay "on" again. If the computer loses the "engine running" signal from the crankshaft sensor, then it cuts off the fuel pump relay. It is for safety: If you are in a severe wreck you don't want the fuel pump running if the fuel lines are damaged, so the computer shuts it off if the engine is stopped for any reason.

If your pumps are not running when you first try to start the car, then I would suspect that the circuits in the fuel computer that supply the signal to run the relay have failed. There is an entry in the FAQ about that. You can build the little add on circuit that is shown, and that will work. I did and it worked for about a year. But eventually either the rest of the computer failed or a wire from my add on circuit touched something it shouldn't have and caused a failure. I would suggest checking to see if the computer is energizing the relay when you try to start the car. If not then the computer is probably bad. There are diagrams for the computer wiring in the FAQ, I think. You want to check the wire that runs the pump relay to see what it does when you turn the key to the "On" or KP II position after the car has been sitting for an hour or so. Based on my experience, I would recommend just buying a replacement computer if the computer is the problem.

If the computer is running the pump for a second or so, but won't let the pump run when the car starts, then it is more likely the crank position sensor that is not letting the computer know that the engine is running.

If you need a computer, search on eBay for a seller named 240salvage, and contact him. He is rhaire from the Brickboard and is a very trusted and reliable source. Very reasonable prices and knowledgable too.
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Scott Cook - 1991 745T, 1986 Toyota Tercel (Don't laugh, it is reliable, faithful AND gets 41 mpg!)

Go to www.stepbystepvolvo.com for free guide to 740 no-starts. It also lists site for 700 fuel injection wiring diagram.

There is no cycling of the fuel pump when the car is running.

I would begin by resoldering the circuit board on the relay.

Randy