Hey everybody, thanks again for the help with my wife's 1993 240 Classic wagon back in thread: http://www.brickboard.com/RWD/index.htm?id=1579953&show_all=1
However, the problem still seems to persist from time to time. The car is fine for a week, and then dead with no-start condition and requires a tow home. In this condition, the car can be started on starting-fluid/ether, so I know it's a fuel delivery issue.

My hypothesis is this, there's a poor wiring connection somewhere for the main fuel pump, and possibly/probably the ground. When there's no pressure load on the system, and the pump is only drawing an amp or two, everything works fine and the flow is good. However, when the pump has to do work (pushing against the pressure regulator), and it's trying to draw a regular current load, the resistance of the connection(s) goes up and the pump voltage drops and browns out. I haven't proven any of this yet as I'm trying to minimize laying in the snow under the car unnecessarily. I've cleaned almost all the ground connections during this project earlier, but I think I missed the main fuel pump. All of my Volvo green manuals are buried in the storage unit and I'm hoping someone can tell me where the fuel pump ground is located so I have the dismantle the least amount of seating and carpet to get to it. I do have my Bentley book and the wiring diagram does not show specific locations for this circuit.

Thanks for the help in advance and God bless,
Fitz Fitzgerald.

P.S. For any of you studying or considering pursuing an ASE Automotive Mechanic's certification, one of the test questions you'll have in the electrical section pertains directly to the situation above. It might be phrased like "What is the likely culprit if a tail & brake bulb glows with the parking lights on, but completely dies when the brake pedal is pressed." The answer would be something like: "A poor ground connection at the bulb or in the wiring has a resistance increase when additional current is applied and opens the circuit."

Thanks for the help everybody, and thank you Art for mentioning this way back in October and me missing it both times (then and again on Friday when I scanned over the message again).

With a somewhat warmer Sunday afternoon (still below freezing, but close enough that sunlight warms tools & parts to above-freezing temps) I've managed to accomplish the following checks and begun to narrow down the culprits:

1. Getting good pump voltage of 12.4 v while cranking at the white 2-pin pump connection (under carpet below the rear seat on driver's side, thanks everybody for the info!) Note, this is measured with the pump attached and hopefully running properly, as I back-probed the connector with some of my wife's sewing needles.

2. Verified pulsed voltage to the injectors confirmed, also by back-probing an injector wiring connector.

3. Disconnected the gas return line from the back fuel pressure regulator and observed no fuel flow. -thus there isn't sufficient pressure in the line from the fuel pump. -if any at all.

4. Tapped the fuel main fuel pump carrier assembly with a hammer. Cranked on the car and it started!!! Yay!

With this knowledge, and reviewing the helpful posts from Machine Man and Pageda back in October, I'm suspecting the Pressure Accumulator or the Main Fuel Pump itself.

Now, here's the question that I'm up against. Where is the pressure accumulator in this system, or does the pump not have one? Is the check valve mounted inside the pump as the Bentley book terminology implies for the LH systems, or is it the removable hexagonal protrusion at the end of the pump assembly as my intuition tells me. Machine Man may have been dead on correct, as I can't confirm or deny if I've been swapping or keeping the original accumulator/check-valve while I swapped pumps several times last year (assuming the accumulator is the hex-assembly at the end of the pump).

Sorry I didn't have my ear next to the pump earlier this week to check operation. I could have jumpered wires to the white Molex connectors or manually closed the main fuel relay with my fingers, but I've been taking some short-cuts today and my wife was unavailable to try cranking while I was under the car (she's frequently breast feeding our 1-month old daughter while I'm troubleshooting).

Thanks for the help everybody, and for the advice and guidance as well. God bless,
Fitz Fitzgerald.

Hi Fritz, glad to see you have made progress past changing around fuel pumps. I am sorry it is so cold there now even though you say its warmer.... For the Tools!

Thumping the pump may have jarred the the brushes inside the pump or the connectors on the outside of the pump.
I had this issue once and was not convinced, which one, may have been the problem, so, I just changed the pump out but kept it old for an extra spare with a note attached. It was changed a few years before I purchased the car according to some maintenance records.

Do you have any ideas on how old your pumps are?

As a side note,I was able to squeeze the the internal clips of each connector on the pump a wee bit to "quell" that concern somewhat!



The check valve is on the outlet side of the pump and is hex in shape for wrenches. If you take it loose to check for trash inside it you should not be able to suck through it in one direction, at all!

The large filter mounted alongside the pump of the tray is down stream of the pumps output. It is a combination affair or both filter and accumulator as far as I know. Its big enough to hold more than just some filter media necessary to strain gas.
It about twice as big as the K-Jet unit of the past and they were given both names then with a (/) slash in some reference manuals I have read over the years.

Jumping the pumps as Art posted in this thread is best thing to do. I use a long lamp cord wire with a toggle/wall switch. This way you get hear how both the main & tank pumps start and run while underneath the car, listening for any hesitation from them. It checks the whole circuit rearwards.
You can cycle them off/on easily and there is a bonus of being able to look for any tiny seepage that can come out from under the copper gaskets.

The fuel filter ends can be a real pain to get cinched up. I have actually had to use a impact wrench to get the final tweaking turn on them quick enough. That's why they are a PITA to get loose. Like wise my filters stay on for a very long time. At the same time, I stay particular about how old my gas gets and where I buy it!

I avoid small volume stations an those around valleys where aquifers might be, you know, like rivers, creeks and lakes.

Buying gas is better done when you are using some Knoll...edge!

Keep your tools warm!

Phil

Hey again Fitz,

(1) 12.4 while cranking? You have a *really* good battery. ;)

(3) No bypass from the regulator makes sense if the pump wasn't running. Much easier to hear the pumps if you don't try to start the motor. Just fashion a jumper between the battery hot at fuse 7 and fuse 4 to turn them on. I say fuse 7 instead of the oft-suggested "fuse 6" because I don't recall if your 93 is early or late production. In late prod. 93's fuse 6 is not used.

(4) Hadn't considered you might have a "bad pump" as you talked before about just having replaced it, right? Check your work is a rule that finds most of the problems I ever have to be created by, guess who, me.

--
Art Benstein near Baltimore

What engineers say and what they mean by it:
"Essentially complete."
Half done.

Fitz
No accumulator in at least LH 2.2 and 2.4, the check valve is attached to the discharge side of the pump. I discovered a problem with my daughters car many years back by lightly tapping on the main fuel pump. I got it running with the tap and she was able to get home where I replaced the pump right away.
Dan

Fitz, if you lift the rear seat and catch the voltage at the yellow/red "browning out" there are a few places likely to find the high resistance connection. On a '93, you have your choice betw early and late.

Early harness runs the fuel injection (pump and all) through fuse 6, and it is never going to be as low as 1A and still run. If late prod, there's the PAL fuses under the hood.

Both places are known to have local heating from high contact resistance. There's a third area affecting model years 91-93 - at the Molex type connector between cabin and engine harnesses, under the glove box. All these spots are the result of moisture.

Edit: Dang, I see I had already answered precisely this in October's thread:

"Hey Fitz, can't quite express my delight in hearing you didn't give up on the RWD Volvos for something more Detroity."

"Anyway, here's what I would do -- and knowing you, you probably did it already and just didn't tell us. Given you've already assured yourself of good connections to the main pump (by changing it several times) you could trust a reading on the pump's terminals to an easier-done check under the rear seat where the connector is above the pump. Yes, I suspect a lousy connection, not a failed part. The connection is usually at the fuse, its terminals, the crimp on the faston, but depending on whether your 93 includes those PAL fuses at the battery, the list gets even longer. There's a 12-pin Molex between cabin and fuel harnesses above the passenger's knees too. Anyway, I suspect if you have good voltage at the pump, you'll have good fuel pressure. And I don't blame you for not having the adapter you need to measure it at the rail -- you need some kind of sharp 90 degree adapter to get a leak-free (read safe) connection to that Schrader."

--
Art Benstein near Baltimore

Q: Do you know how an electrician tells if he's working with AC or DC power?

A: If it's AC, his teeth chatter when he grabs the conductors. If it's DC, they just clamp together.

unless they changed it in the 93, the ground for the main fuel pump is under the rear seat, drivers side.

drivers side under the rear seat under the carpet is the harness that connects the fuel pump to the fuse box.

The ground for the main fuel pump is under the rear seat on the drivers side. There is a single spade connector in a black housing (+12v, probably yellow wire) and a black wire terminating in a ring terminal, bolted into the body. It's the only wiring under the back seat on that side, so should be easy to locate, especially with a wagon.
--
'82 245 B21F-MPG-LH 1.0, '83 244 B21FT-K-Jet, '86 244 B23F-LH 2.0