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So, I still don't get it. And, Bruce, I'm certainly not saying you're wrong (read on and you'll see why), but I just can't make this #6 fuse thing make sense to me (I know trying to make sense of a Volvo electrical system is a quixotic quest at best, but...). Here's what I found out:
1. As ascertained before, the fuse panel label says #6 is for the main fuel pump relay (not the pump itself). The owner's manual agrees.
2. The diagrams in Haynes show that the pwer comes directly from the battery, through the junction block under the hood to the #6 fuse. From there, it goes to the #4 fuse and on to the in-tank pump, the ignition system brain, the FI brain and the main fuel pump relay. When the relay is active, it completes the circuit directly to the fuel pump. Effectively, then, it shows the #6 fuse as bein between power and pump.
3. I stopped by two Volvo dealers today in two different states (not the only purpose of my trip--I'm not quite that obsessive). At one, I asked the service guys, and they all concurred that #6 is for the fuel pump relay. At the other, I just asked to see the wiring diagrams in the Volvo service manuals. As I suspected, the diagrams in Haynes are reprints of the Volvo diagrams (not at all unusual). Another image in the Volvo service manuals shows the power flow throught the #4 and #6 fuses, and it concurs with their stated purposes.
4. BUT-- on Bruce's admonition, I looked at my own #6 fuse with the kick panel removed. It really did not seem to have anough wires hooked up to it. Just one red one. So, I checked the voltage on the red wire at the relay. 12.56 volts. Then I pulled the #6 fuse. 12.56 volts!
So, all I can conclude is that all of the sources do not agree with my observations of reality. Again, I understand that tring the apply reason to Volvo electricals is a fool's game, but I just don't understand why all of the sources I consulted would be wrong. I also don't understand why Volvo would leave such an important circuit unfused, or why they would put a fuse there, hook up a wire to it (either from power or to some device), then leave it hanging.
Can anyone out there relieve my burning curiosity as to the underlying logic, or lack thereof, of the whole thing?
-EdM.
'90 240DL Wagon "Lola"
'72 1800ES "Galadriel"
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Ed,
Please give me a page reference in your Haynes, so I can see what diagram you are looking at. Maybe I can find what's tripping you up.
You've already discovered what I was saving for my next salvo — the fact that fuse 6 has power in, but none out.
But your '90 FI and Ignition systems are fused — by the 25 amp blade fuse near the coil. In 91, as I said, that 25 amp fuse was done away with, and replaced in the circuits by good old #6 (upped to 16 amp I think).
I wish you'd dump the Haynes for a Bentley manual. It's been offered for as low as $30 by eeuroparts, where going over $39 with a few parts and the shipping is free.
I've been dabbling with 240s since 1990. I do have a Haynes from that period (and a later one) but they are virtually untouched compared to my dog-eared Bentley.
Try finding the "On Board Diagnostics" info in your 1976 thru 1993 Haynes. It sure raised my blood pressure earlier today. As you know there are OBD codes for both Fuel Injection and Ignition (Hint: Don't bother looking in either of those chapters.) And when you do find it, there will be nothing on the Mode 2 and Mode 3 capabilities. For Haynes, they don't exist. Nor for you either, if Haynes is your only reference.
--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.
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Bruce wrote:
> Try finding the "On Board Diagnostics" info in your 1976 thru 1993 Haynes. It
> sure raised my blood pressure earlier today. As you know there are OBD codes
> for both Fuel Injection and Ignition (Hint: Don't bother looking in either of
> those chapters.) And when you do find it, there will be nothing on the Mode 2
> and Mode 3 capabilities.
Yeah! I mean, it kind of makes sens that the OBD codes are in a chapter on the engine management system, as are the sensors (all except the one I needed to replace, that is, the rev sensor, which is completely absent). But as for modes 2 and 3, I found about them from, yes you guessed it: this forum.
Amazon has the Bentley manual for about $31, so I think I will finally do that. As I mentioned previously, the Haynes books were great for me for older simpler cars I have owned, but their deficiencies become apparent as the amount of information needed for newer cars outstrips the amount of content they want to provide at their price point. Such is the publishing industry. Could be worse, though: I have a Chilton book I got with my 1800 (I would never actually buy anything from Chilton myself) that tries to cover every Vovlo model from 1970 throught 1980. That's right: 140, 160, 1800E&ES, 240, 260, gas and deisel, all in a book no bigger than the Haynes. At least what you can find in Haynes is usually correct. It's pretty bad when the precious little bit of info pertaining to your model you do find in that Chilton book is wrong (like: use the throttle stop screw on a d-jet to adjust the idle--WRONG, WRONG, WRONG!).
Anyway, I'm 60 miles from any of my books now. I'll post those page references when I get home.
-EdM.
p.s.: It does occur to me that the diagrams I saw, both in Haynes and at the dealers (the same diagrams, recall), make no mention of the 25 amp fuse. Curiouser and curiouser.
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Here, as promised, are those page references from Haynes.
4A-24 Shows the LH 2.2, in which power is supplied directly from the battery to the relay. Post relay, the in-tank pump is fused on #4, but judging from this diagram, the main pump is not fused at all. As this is an LH 2.2 system, the #6 fuse has nothing to do with it, either on paper or in reality. Note: this diagram was not in the Volvo service manual I saw, although the CIS before it was, as was the LH 2.4 and LH 3.1. I didn't get the logic there, either.
4A-25 Shows the LH 2.4, in which, according to the diagram, power is supplied from the battery to the junction block (the one between the 25A fuse and the headlight relay, right?), to fuse #6. From the other side of fuse #6, two (not one, but two!) red wires go to exactly the same place, connecting just a few inches and a few corners away, then splitting off to supply power at terminal 4 of the FI brain, terminal 5 of the ignition brain, and the fuel pump relay. Power out of terminal 5 of the relay (connected to power when the relay is tripped), goes to fuse #4, on the other side of which, it flows out to heat the 02 sensor and power the in-tank pump--BUT--before going through fuse #4, it glances off to power the main pump. Note: the 25A fuse is not on this diagram at all, just another clue that it is incorrect.
4A-26. Shows the LH 3.1, in which all germaine points on the diagram are the same as for the LH 2.4.
It also occurred to me that, if the power to the FI and ignition control units really did go through fuse #6, then there's no way the car would start or run with fuse #6 out. So, the published fuel pressure relief procedure can't be correct. I guess that bears out the idea that my fuel pressure regulator really did need to be replaced.
So, you've got a convert in me, so to speak. I am still forced to wonder, though: how can all these published sources, even straight from Volvo, be so blatantly wrong? If it weren't for the info you provided, and for the obvious fallacy in the above paragraph, I would have assumed that my car was the victim of a hack modification to the fuel system wiring. I'm relieved to find that's not the case.
-EdM.
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Ed,
Our Haynes books must be different editions. Mine has the LH 2.2 diagram on 4A-28. It shows item "F" (25 amp fuse) between the battery and the relay. So the pump (and system) are fused, and the diagram appears to be correct for LH 2.2., except that in the U.S. it lasted thru '88—not '86 as the caption reads.
My page 4A-29 has the LH 2.4 diagram as you described. Compare it to Art's LH24_1.jpg, and you'll see the fuse wiring is as I described, where only fuse 4 plays a part. The caption is also wrong (for U.S. cars). Our LH 2.4 began with the '89 and continued till the end in '93. So Haynes must be showing a Volvo functional diagram for a European spec car ( a typical Haynes touch, IMO.) Nice catch on the missing 25 amp fuse.
" It also occurred to me that, if the power to the FI and ignition control units really did go through fuse #6, then there's no way the car would start or run with fuse #6 out. So, the published fuel pressure relief procedure can't be correct." (I think that's where I came in.)
Art and I have discussed these "functional" diagrams before. My opinion is that they are more apt to have errors than the "back-of-the-book" diagrams he mentions. You'll see those in your Bentley, and will find they too have a few quirks. Just post your questions as needed.
--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.
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Good old Haynes used to publish all the diagrams in older European editions, including those for North American models. At it's worst, nearly 2/3's of the mid 80's edition was revisions.
They improved a bit when they bought out a company called 'Autobooks' and rationalised the manual - leaving out all but UK spec diagrams. They don't seem to list anything different after 1986, just '86 - on', so maybe you got all our wiring diagrams for a bit of fun.
Maybe the Australians got yours!
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Good old Haynes used to publish all the diagrams in older European editions, including those for North American models. At it's worst, nearly 2/3's of the mid 80's edition was revisions.
Yes, I have no complaints about their 120 and 140 manuals -- nor even the 240 edition for 1974 thru 1990. That one served me well till the Bentley came out.
But I will never condone their method of (stupidly, IMO) referencing Section Numbers rather than page numbers in each chapter's content list. No doubt it makes revisions easier for them, but the text-processing software from the '80s used to handle page number updates OK as I recall.
Nor do I think much of slipping the (incomplete) OBD I text into the "Emissions and Engine Control" chapter instead if the more relevant FI and IGN chapters as Bentley has it.
IMO, the Bentley's organization and ease-of-access alone make it well worth the price.
But that's just me. An old and grumpy fan of Andy Rooney.
--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.
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One of the most confusing things about Volvo's diagrams is the inclusion of multiple versions of the car on one sheet. Your eyes follow schematic traces for European K-jet versions of the B-230 or even B-200 while you are trying to match what you see in your LH2.4.
Fuse 6 on a US '90 is like your appendix - goes nowhere or may be removed altogether.
--
Art Benstein near Baltimore
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Not on the diagrams I saw at the dealer: they were very model specific, with seperate pages for the American market CIS, Canadian market CIS, LH 2.4 and LH 3.1.
-EdM.
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Hi Ed,
You were looking at the functional diagrams in the Wiring Diagram Manual. They show you a particular function, and yes, it is specific to market, but these are not the drawings most of us have casual access to.
The two long pages in the back of that book represent the complete wiring diagram and these are the only ones reproduced by the aftermarket publishers for each model year change.
Even the Volvo WDM pages are not error-free. However, the 25A blade fuse under the hood is shown on the detailed drawing for LH2.4 as item 212 (in line fuse) powering the two computers and the armatures of both relays in the fuel injection relay module.
If you need this page I'll be happy to scan it for you.
--
Art Benstein near Baltimore
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Thanx, but no need to go to the trouble of scanning and sending it. One bit of info, though,if you could: are the diagrams you're referring to in the Bentley book? I finally ordered one last night, and one of the things I've been hopeful for is that it would include complete wiring diagrams.
My 1800 has its entire wiring diagram on one page in the owner's manual, but gone are those days! And here's a fun exercise: the Haynes MGB book includes complete wiring diagrams for every interation of that car. It's neat to see the development in complexity of the system over 18 years from its utter simplicity in 1962 to what I, at least, consider silly overcomplexity by 1980.
-EdM.
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Wow! Those are totally not the diagrams I saw at the dealers, the difference being that those are accurate! Pretty scary. Once I feel I've let enough time pass since the last time I bugged my mechanic for free advice, I'll run it past him, just to hear what he has to say about it.
Hey, now maybe I'll hook something up to my #6 fuse. It's powered, right? And directly off the battery, so it's a completely isolated circuit. Oh, the possibilities.
-EdM.
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Let's just hope the reverse of my shoddy automotive analogy doesn't apply lest some physician find a new use for the appendix.
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Art Benstein near Baltimore
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