I had to have my son's 97 850 (130k miles) wagon towed home on Friday. It started, then died within a couple hundred feet. He cranked it until the battery was dead. The battery is new and took a charge OK.

This morning I started troubleshooting with checking fuses. The fuel pump fuse (#2) was blown. I put a new one in and heard the pump come on and it started right up. Repeated 3 times and the fuse blew again.

My questions... is the fuel pump a routine failure part? Is it usually the pump or a relay? At $315 at FCP I don't want to put fuel pump in it if we don't have to.

I am at least pleased that you don't have to crawl underneath to replace it!

Thanks for your help

Tim Benner
Dayton, Ohio

 

I would think it's a bad relay, but I'm not expert on this by any means. I have never experienced this problem myself, but I would start with doing the relay. Lets see what tech says before doing anything though.

 

A way to find out is to jumper the relay and take it out of the equation. Fuse #2 feeds both the pump and the control circuit on the relay so it could be either. If you remove relay 103, you need to remove the fuse box top to get to it, and look at the bottom of it there are 4 terminals. Molded into the plastic next to each terminal is a number, they should be 31, 31b, 15, and 87. Place a jumper wire between the sockets associated with terminals 15 and 87 and then see if the fuse continues to blow. If it does, the problem is the pump itself. If it doesn't the problem is the relay.

...Lee

 

It sounds like you have a short somewhere which is blowing your fuse. I'm not an electrical guru so I honestly have no clue where to start on that.

A relay can be soldered for a cheap fix (2-3 dollars if you already have a solder). That beats paying 50 dollars since it's a dealer only part.

Secondly, the fuel pump indeed is a pretty high failure part but you only need to buy a fuel pump insert (the actual pump) which is around 100 bucks. The $315 includes a new assembly which you most likely do not need. You can go with an OEM, or even go aftermarket in which you will get a higher flowing pump at 255lph. It shouldn't make a difference in gas mileage since all unused fuel is returned to the tank.

 

Hi Ozark Lee,

Good sound, advice once again, but in the event there isa short circuit in the electrical wiring -I would add the following:

Procedure 1:
(1)disconnect the fuel pump at the tank
(2) replace fuse (this will check out all wiring and componentsright back to the fuel tank.)

Result A:
(a)fuse O.K -fault at fuel pump. Removefuel pump from fuel tank and bench test.
(b)fuse ruptures - short circuit in electrical circuitpriorto fuel pump.

Procedure 2:
(c) remove fuel relay

Result B:
(3) fuse O.K -replace fuel relay.
(4) fuse ruptures - short circuit in associated electrical circuits.

Procedure 3:
(d) Split the wiring loom carrying fuel pump circuitry at the most accessablepoint approximately half way back to the fuel tank and test.

Result C:
(5) fuse O.K - short circuitis in disconned part ofelectricalcircuit.

However, if thefuseruptures thencontinue testing in a similar manner splitting (disconnecting) the electrical circuitsuntil theactual area oftheshort circuitcanbe pinpointed accurately (appropriate Volvo wiring diagrams that show make up of wiring looms, connectors, connection points etc. will be needed). It then becomes the nit-picking procedure of visualy examining and testingeach relevant individul wire in that particular part of the wiring loom.

While I would be having a long, hard look at the fuel pump (it does start 2 or 3 times before the fuse ruptures) I hope this additional bit of information may give tbenner somemore ideas onhowto findthe fault in his son's car.

 

Thanks everyone!

I really appreciate the response and especially the step by step procedure. I'll have a look at it tonight and see if we can determine what part is faulty!

Tim

 

I forgot to mention the capacitor(s) in the fuel relay often go faulty (I think Ozark Lee has posted a step-by-step capacitor replacementinstruction on this forum).

A faulty capacitor will do either of two things (a) open circuit or (b) short circuit.

It just may be possible the capacitor(s) areshort circuiting sufficiently enough to blow the circuit protectionfuse on an intermittent basis.

 

Checked it out last night... With the fuel pump disconnected no fuses blew. We tested that with a 10-15 cycles, leaving it on for a few minutes.

With the fuel pump connected it was OK for the initial prime of about one second. Once the car started the pump would start, then the pitch of the pump would rise and the fuse would blow within about 10 seconds. Sounds like the pump to me...

I have a pump on the way from a local parts house that has been pretty good to us on Volvo and MB parts. The pump & screen insert is $180 but I'll have it today. And while thecargo floor is out we're doing the rear shocks & mounts. They gave me Bilstein Tourings for 60 each which seems like a pretty fair deal.

I'll post back on how it turns out.

Tim

 

cool. let us know how it goes...

 

Success... well mostly. The new fuel pump is in and not blowing fuses. The car starts and runs fine. One shock mount was broken back there so it was a good time to be working in that area.

BUT... We had been having problems with battery drain. We thought that it was the Central Locking circuit and pulled the fuse. So before I hooked the battery back up I put an ammeter across the cable and battery post and it is drawing about 500ma with everything turned off! So the kid's not driving quite yet. But when he does he'll love those new shocks.

I left the ammeter connected and pulled all the fuses one by one and the current draw never wavered. So whatever is leaking current is not going through the fuse block.

Next, after our shakedown drive I left it idle facing the garage door. Revving it just a little you can hear the fuel pump change pitch to keep up with the fuel pressure demand. Here's the worrisome thing; when the pump is working harder the lights dim until the pump reaches its regular idle pitch. That can't be right can it?

Anyone have any ideas?

Thanks again to all!

Tim

 

Tim,

Something still isn't right if you are hearing a change in pitch on the fuel pump. I don't have component level schematics on the fuel pump relay but my understanding is that the circuit on the fuel pump is set up to:

a) Precharge the fuel system the second that the key hits position I and then time out and quit running if the run (position II) is not hit after a designated time.

and


b) In the run position the fuel pump should run continuously at the same speed and let the fuel pressure regulator and the fuel return lines deal with any excess fuel pressure or volume.

...Lee

 

Lee,

It sounds like I need to locate that relay. The pump behaves normally at position I as it runs for a second or two and stops. Then at position II it stops if the car is not running. If the car is running it maintains a constant pitch except when revving.

I wonder if this behavior and the battery drain problem are somehow related.

Tim

 

.025 is about the max for an Amp draw from the car.
Anything aftermarket in the car?
Also with the car running check how much voltage is at the battery. it should be 13.5 or a little more.

If it is pretty low probe the positive wire before the terminal and see how much voltage is there.
See how much you loose through the terminal. The terminals solder joints go bad. That could be leading to some of the voltage problems.

 

I hope the attachment would be of some ref.

http://www.fcpgroton.com/volvo850fuelsystem.htm
http://www.eeuroparts.com/searchresu...8&cat=1028


JPN

[IMG]local://upfiles/6892/BAF45FC4B517493FB0968CA41BC80687.jpg[/IMG]

[IMG]local://upfiles/6892/D4CA75DE0AEF4E09990B8CFFD2F39439.jpg[/IMG]

 

Thanks Tech and JPN. It looks like the fuel pump relay will be easy enough to replace. I'll check the battery voltage after work. There is nothing aftermarket on the car.

The more I thought of the headlights dimming and fuel pump pitch dropping when the car is revved, the more odd it seems. If anything, one would expect the lights would get brighter as the alt should be charging more with higher revs.

Tim

 

We did some voltage testing tonight. My only working meter is an old analog so we may be off +/- 0.5v. I'll pick up a digital for the weekend.

Battery disconnected - 12.0
Connected & Ign off - 12.0
Connected & Ign on - 12.0
At idle - 13.5
1500 RPM- 13.5
2000 RPM - 13.5

The readings were the same from the battery posts and cables

It is still leaking 500ma with everything turned off.

Since we know the current leak is not through the fuse block can anyone suggest where to start looking next?

Thanks again for all the help.

Tim

 

Find the alarm relay under the dash and try pulling it. I have seen them go bad and cause a draw.

 

Thanks, Tech!

That sounds promising. Can anyone help with locating this? I have a Haynes manual and Vadis disc which haven't help in locating it so far. I could just pull the bottom panel (assuming it's on the drivers side) and start pulling relays.

I'll let you know what we find!

Tim

 

I wonder if this is the alarm relay, doesn't look fancy enough to be a "module" but is surely located under the dash.


JPN

EDIT: I think I was right; see 2nd pic, it indicates the same relay.

[IMG]local://upfiles/6892/13E1C027C0E04AE7AD11EB7D54B1952A.jpg[/IMG]

[IMG]local://upfiles/6892/E9A218070807431F9E30C5F3528F414B.jpg[/IMG]

 

Perfect! Now if I could just find a reason to leave work early and pull it...