comparing fuel system relays

I have searched and looked over the various diagrams here and didn't find exactly what I was looking for...so if its there, just please point me in that direction and accept my apologies. This may be a stupid question to begin with, but I just want to double check something..... I am upgrading to a newer ignition / electronic fuel system on an older car using a later factory setup. Everything has been mapped and the harnesses made - so far so good. Now I am at the power supply setup. The fuel relay is different but has the same connectors (30, 85, 86/1, 86/2, 87/1, 87/2). Do these designations have the same purpose on every relay (i.e., does "30" have the same function on any relay labeled "30"?). From what I can tell, it does, but I want to make sure as I'm going to modify it a bit to split the power load on the main fuel relay. Thanks much. :)

They are supposed to. They are defined in DIN Standard 72 552. You may find my ramblings on fuel pump relays - ie, they should be ECU controlled else alternator or air-flap or spark, but NOT simply IGN +12V, or oil pressure.

Yes, they are ECU controlled. What has baffled me is that they lump both fuel pumps (in tank and chassis) plus the O2 and injectors all onto one circuit. Typically one of the feeds on the relays either discolor or just burn/melt from the load over time. I want to use the fuel relay (which is light duty IMO) and use it to simply switch on (2) heavy duty 40A relays that will power 1.the pumps and 2.everything else (normally on that circuit). And of course all the relays will be fused. Is 87/1 the same as 87a (and 87/2 = 87b)? IIRC, 87 is the supply feed to the component. So is 87/1 and 87/2 a switch/feed to two separate components? I could cheat and go to a guy I know who has done this conversion and get his notes, but to be blunt, I don't like how he did it and need to crash-course learn this on my own to do it (IMO) better/correctly. Thanks again.

Oldspark, I thought we got rid of the 86VW but am I being paranoid.

Don't mention 1985 vw quantum, bad relay or fuel pump? ...!!! Though I was going to reference it for the KAE 3.300.210 relay - it's a spark-sensing fuel pump relay that also powers on during initial power-up. But that's for (IMO in general) stupid EFI systems that do include the fuel pump control. Else for carby vehicles that have electric fuel pumps. The main point with fuel pump relays is that they should be controlled by an engine running signal (eg, alternator, spark, airflap, ECU) and not by raw IGN +12V or oil-pressure (both of which fail international safety standards and most competition rules). (Besides which oil-pressure to kill the fuel supply is moronic - it should kill the ignition! Or fuel/air for diesels.) handyguy, it makes sense to all be on the same circuit logically - ie, one fail, they all fail. But that doesn't mean the one relay. In fact often injectors are on their own relay & fuse and fuel pumps on a separate relay & fuse. In part that is because fuel pumps must energise when IGN is first turned on; injectors don't - hence 2 separate circuits. I like your DIY approach. And I like that you question (ie, don't like) the other solution. But why not describe what YOU want, else what you don't like about the other solution. Mind you, my preferred "universal" solution is in that abovementioned unmentionable link (SPST relay(s) and diodes from crank signal, alternator charge light or airflap etc). But in your case, the ECU does control the fuel pump so I presume you have concerns/objections about the external wiring. [It's not a Delco with an external "backup"(sic!) for the fuel pump - namely the oil pressure switch (morons!)..???] Hopefully it is merely the sharing and stressing of the relay... Admin note: Inclusion of "relay" in the above link kills the underlined blue text... "relay" is hyperlinked (whatever they call it these days)

Dang! I forgot my original reply. I'll blame that on Howard. (Sorry mate, I think THAT thread left me scarred, though having just re-read voltage drop problem, what battery to buy? ....) handyguy, maybe docs like autoelectricsupplies.co.uk-bosch_terminal_designations.pdf might help. Not that I deal with those numbers etc - hey! I only learned relay 30, 85, 86, 87 etc since staring on THIS forum! - but I'd assume the /1, /2 etc to be "junctions" off the same "terminal". That's not the same as saying 87a is a junction off 87 - 87 is the NO contact (connected when the relay energised) whereas 87a is the NC contact (Normally Closed - ie, relay de-energised as in its "normal on-the-shelf" contact position). But I tend to design ground up (to meet top-down designs) else have to work out those DIN numbers so I design "functional" circuits - ie, I schematically draw the circuits - traditionally I never use(d) "physical" representations with 30, 87, 87a pin numbering. Hence I work from the description of what is wanted. (I prefer not to infer the desire from a supplied circuit diagram, and I'll rarely decode a "wiring diagram" unless essential to me.) Howard - no, "design ground up" was not a pun - you know I EARTH my designs. But they do burn top (non-earth) down. [ I was going to say +ve down, but having worked with telcos where -ve is up for their +ve earth/ground systems... And I'd rather not comment on +ve chassis vehicles... ] Dear oh dear - how some people have their bits of hijacking humor. If only they knew how it confuses some!

And don't forget good all 87b, essentially a twin SPST relay sharing a coil but separated outputs, think early hazard flashers.

Thanks for all the input....its priceless to me. The car I am rewiring is a late 80's Volvo 240. They came with a Bosch ECU, but a Chrysler "shake and bake" ignition that like many super models, does not age well. I removed the harness from a late 80's 740 model as it has the Bosch EZK ignition system in it. The 740 system is also used by many who own older BMWs, Porsches and Audi's because its very adaptable, stand alone and makes the upgrade to turbo very easy. What "others" have done in the past is to try to adapt the 240 system and wiring harness to the 740 set up.....mingling apples and oranges if you will. I prefer to lay in the 740 system and keep the color codes, routing, etc all OE - for diagnostic purposes if not for anything else. It keeps apples as apples. By "adapting" it as they do, there is also alot of mis-routing of harnesses. I also prefer a stock clean install. I solder, heat shrink, use OE clips and mounts, etc. When its done you would swear the Swedes did it on the assembly line 25 years ago. When I figured how to adapt the later cruise controls and AC systems to the older cars, I made a "handbook for dummies" (myself included as if its 5 yrs between upgrades, I want something as simplistic and plain English as I can get). I want to do the same with this. Many have done the EZK upgrade, but IMO, in a cobbled sort of way. The "new" system will still be on the same "controlled" circuit - that is, the OE fuel relay. But instead of the relay itself handling all that current to supply the injectors, pumps, etc. (its delivered in a single 10-12ga wire and distributed on two 14-16ga wires...its this contact that fries over time) - it would be used as the switch to activate 2 more capable relays to handle the loads individually. The safety fuel/cutoff features WILL remain intact (one of my prime directives here....sorry, the sci-fi geek in me is showing itself; allow me to remove my rubber Spock ears and continue ). So when the signal cuts off the fuel relay, it would also kill the 2 larger relays handling the fuel system. My hangup in this entire project has been the power supply - figuring it out so that I can modify it. Fortunately, both systems do use the same fuel relay.....now to figure out how they hook up. ?!

Your use of the "main" relay to drive others is an excellent method. Although the main could drive a load and another relay, IMO why not take the load completely off by having it only power other relays? That is a common technique, yet often overlooked. (I think of low-voltage cutouts or multi-battery isolators where the main sensing or control relay could switch other or bigger relays for more batteries or larger currents instead of buying more or larger "sensing" relays!) Your prime directive is excellent - keeping the fuel pump relay operation true to safety requirements etc. And your OEM look is well understood, though "wow!" - most I know will retrofit the entire "donor vehicle's ECU loom"; though that is in ECU-less carby vehicles.    But I well understand the desire and work involved in the modifications. Yes - there is lot's to go wrong, but it can be quite straightforward (still a lot of work though). FYI - I modify my 45 year old vehicle, and although I never cut into the original loom (I make adaptors else run separate wires), I have also started to stick to the original color codes - including adding the new colors pertinent to the newer donor models (from the same manufacturer).

I'll add this to see if its clearer to you than me. I may just be too close or looking at it too long to see the forest for the trees. I've added links to pics of these relays....hopefully they work ok. The fuel relay is wired as such: 30:   Power supply from fuse 85:   Jumpered to 87/1; and an 18ga wire not shown on the schematics-? 86/1: ECU Terminal 86/2: ECU Terminal 87/1: ECU Terminal, and to 86 on a 40A "radio suppression relay" 87/2: 14ga wire to fuel pumps; 18ga wire to O2 Sensor The "radio suppression relay" (no idea why they call it that) is a 40A relay (like the ones I want to use to split the circuit up). They are plentiful and work great - I use them for everything from driving lights to pusher fans for the AC. Its wired as such: 30: Power Supply 85: Ground 86: Switch 87: To component(s) And here's a link to a scan of the OE schematics I'm using. Thanks again.