GM oval fuel pump relay terminals/components/tools?

[dave w]

This is SOMEWHAT pertinent, I hope people are still reading, as I know some of you have test benches.

Does anyone have any idea to A) what this style relay is rated for and B) what the entire injection system draws for ignition 12V while running? I know there will be some variation, but I am working on re-wiring my setup, and realized I'd run pretty much everything off the fuse panel accessory taps. All of those circuits are on 30 amp breakers, yet the fuses for the injection stuff are mostly 10 or 20 amp, which easily exceed the 30 amp breaker rating, yet I've never tripped it.

I would not be surprised to see that GM had a very large safety margin, but I don't want to start using those relays if they aren't rated to handle the load. I'm going to use an ignition hot to trigger the relay, which will then feed a bus on a separate fuse panel. Instead of running 5 separate wires all the way across the truck to feed things like the injectors, O2 sensor, etc. I will be able to run one long wire from the existing fuse panel, and run much shorter wires from the separate fuse panel to the items that need powered. The combined fuse rating will be somewhere along the lines of 50 amps for the ignition switched.

I now realize why the later vehicles are running relay/fuse centers underhood. I could use something like that, but the oval relays seem to hold up really well to water and mud, and if I use all the same ones, I only need to carry one spare, if that.

Standard Motor Products rates their fuel pump relay (RY109) at 30 AMPs.

On my engine test stand, I've operated a complete TPI system with a single 15 AMP fuse for all ignition "ON / Start" circuits.

dave w

[dyeager535]

I appreciate that. I wasn't particularly clear in my previous post, what I meant was that all ignition switched circuits on the injection side are run off of a single 30A breaker, so I'm really unsure of why the fuses are rated at what they are...you have run everything on a 15A fuse, mine on 30A breaker, I can't see any reason why they didn't use a much smaller fuse, such as 5A.

I think I'll be safe then doing what I planned. Probably use a 10ga wire from the battery to relay.

Other option is to use an even larger wire straight to a battery 12V bus bar/junction block near my "relay/fuse center", and use that to power everything short of the fans, to include the ECM which will also probably end up in the same area.

Dave, what kind of intake air temps did/do you see on that setup in your picture? I was curious since I'm running a "cold air" setup I put together, and noted my IAT was about 101* on short duration cruises while tuning. Idle IAT was around 118*. Can't remember ambient temp, it wasn't super hot of course. Will have to re-think my intake routing when I go MAP.

[EagleMark]

My LT1 was pretty close to ambient temps when cruising, but went through the roof sitting still.

[pmkls1]

A couple of reasons for having fuses with a combined rating much higher than the circuit breaker that supplies them all would be that 1: The separate fused circuits may not all have a "demand" for power at the same time and 2: Fuses will "react" very quickly to voltage spikes that can occur when first turning on a device or fluctuations in system voltage for other various reasons and blow. Whereas, a circuit breaker will need a slightly more steady overcurrent condition to be tripped especially the typical thermal type used in most applications.

[dyeager535]

Mark, were you stock induction or "open" like Dave's picture? My plenum never gets hot enough that you can't touch it, but I'm sure that's because the runners keep it fairly isolated. I have a feeling if I went to an "open" setup IAT would climb pretty quickly with the headers.

pmkls1, thanks. Makes sense.

[dave w]

Probably use a 10ga wire from the battery to relay.

Other option is to use an even larger wire straight to a battery 12V bus bar/junction block near my "relay/fuse center", and use that to power everything short of the fans, to include the ECM which will also probably end up in the same area.

Dave, what kind of intake air temps did/do you see on that setup in your picture? I was curious since I'm running a "cold air" setup I put together, and noted my IAT was about 101* on short duration cruises while tuning. Idle IAT was around 118*. Can't remember ambient temp, it wasn't super hot of course. Will have to re-think my intake routing when I go MAP.

The factory uses 16 AWG for the battery power to the Fuel Pump Relay. I think 12 AWG would more than enough overkill to supply battery "+" the Fuel Pump Relay! The "+" wire to the Fuel Pump has a 15 AMP fuse for the engine in the above link. I used a factory "Fuseable Link" (12 AWG) to supply battery "+" to the Fuel Pump Relay, Computer / ECM and the Alternator (Bat terminal) for the engine in the above link (similar to the way the factory supplies battery "+" the service items previously listed).

I don't have the data logs for the test engine, so I can't answer the MAT temperature question. I think the test stand MAT data would not be very accurate, because the engine was not in a vehicle.

dave w

[pmkls1]

pmkls1, thanks. Makes sense.

No problem, it's rare that I can contribute rather than reiterate.

As far as your MAT inquiries go, "open" setups aren't optimal for any reason other than making installation/repair simpler. I will snap a pic of my rigged setup in my TBI application that is open for an example and post it up later. It is only this way due to hood clearance issues and permanent plans involve a WAY different induction setup altogether. I have the factory IAT ziptied to the side of the air filter to provide a true reading of the incoming air temps and see fairly mild readings in 90+ degree ambient temps ONLY because most of the air is coming in through the opening in the stock "power bulge" hood. Just remember IAT/MAT temp readings need to be an accurate measurement of the actual incoming air in order to allow the ECM to truely adjust fueling properly. Cooler is obviously better, but if you are tricking the ECM into thinking the incoming air is cooler then you are completely defeating the purpose of the sensor. I'm sure you're already aware of all that, though, as you were just inquiring about others were seeing with particular setups.

Regarding the wire gauge I agree with Dave that 12ga. is more than sufficient for the 12v supply to the fan relay. I also like the idea of using a junction block or similar setup near to or integrated into the fuse block supplied with a fairly large wire to distribute power from. For all ECM functions short of the fuel pump and cooling fan relays the 30 amp breaker is more than sufficient, but I have never measured the actual power draw of the fuel injection system on any vehicle to have an idea of what the actual requirements are. I would prefer/recommend to use a setup like we are describing for installing fuel injection into a vehicle that was originally carbureted and avoid the original fuse block as a source. I do, though, tend to be fairly obsessive about wiring in general as I originally started my "professional" technician career as a light body specialist at an Olds/Cadillac dealer and with the complexity of the electronics systems found in Cadillacs I was never short on work and acquired a lot of experience at an accelerated rate.

[dyeager535]

Man, why do i keep losing my posts? Must be work...

Anyways, Dave, not sure we are on the same page, maybe we are, I was just making sure the 10GA/30A relay would be enough to feed the ignition switched injection setup circuits, to include the heated O2 at some point. Sounds like it will be plenty.

Probably will go with a single larger wire to a junction block from the battery. Although it means just one less wire, it will still be cleaner at the battery end.

I'll have to look and see what kind of mounting I can do with the '727, would be nice to have it in the same location. Not like the old trucks don't have underhood space, but the further out of the way it is, the easier to work underhood.

[dave w]

Anyways, Dave, not sure we are on the same page, maybe we are, I was just making sure the 10GA/30A relay would be enough to feed the ignition switched injection setup circuits, to include the heated O2 at some point. Sounds like it will be plenty.

Probably will go with a single larger wire to a junction block from the battery. Although it means just one less wire, it will still be cleaner at the battery end.

My thinking is, the 10 AWG wire is nice, but not necessary. Using a wire size larger than necessary is Ok. I often salvage wires form the junk yard, mostly to keep the "Factory Look" or "Factory Color Codes" to the wiring work I do.

dave w

[dyeager535]

I used to salvage a fair amount of wiring myself, but time has been so limited anymore, I don't get the chance. Plus I always ended up with wire 1 foot shorter than I needed!

I browsed around online a bit, and mouser appears to sell just about any color wire out there, EXCEPT the pink/black. Hopefully I don't need long runs anymore, so the shorter sections should suffice.

I concur, keeping factory wire color is simpler, and I prefer it, although I always double check with a meter anyways.

[1project2many]

I would like to add a consideration. When connecting all circuits through a single high amp fuse, there's a high risk that a single circuit with a small peak current draw will be destroyed if there is a malfunction in that circuit. One example, if two TBI injectors are connected through a single 5A fuse then a short to ground on the ecm side of the injectors may blow the fuse before the injectors overheat and fail. But these same injectors tied to a 30A fuse would fry without the fuse ever failing. Another example: If the ECM ignition power is connected through a 10A fuse then an intermittent short on that wire will quickly blow the fuse but the same condition with a 30A fuse may cause the wire to warm up enough to melt the insulation off the entire length of the wire and take any other wires in physical contact with it. What could be a blown fuse might end up as a major rewiring project. I would look at the wire gauge of the components you're powering as a guide to fusing and group accordingly.

For humor: My wife got really frustrated when an intermittent short popped the ecm fuse in her '90 Sunbird on her way to work one day. She used every fuse in the 100 fuse assortment I'd placed in the trunk trying to make the car go. The original fuse was either 2 1/2 or 5A and she used everything in the box including all the lower amperage fuses then working up to (10) 20A fuses, (10) 25A, andn (10) 30A before giving up. When I got to the car it was easy to find the short. All I had to do was follow the one copper wire that had huge bare spots interspersed with melted pink insulation from the fuse panel, under the dash, past the instrument cluster, through the bulkhead connector in the firewall, through the starter and ignition harness to the back of the block. There were probably 15 other wires that had been damaged as well. I ended up getting a used harness and replacing the engine and dash sections rather than try and replace sections of all those other wires.

[dyeager535]

Yes, luckily the Cadillac "fuse panel" my dad picked up for me has 20 mini-blade fuse slots, and there is an assortment of feed terminal. I can feed five fuses with one feed, four with another, three with yet another, etc. So the single 10GA wire will feed five circuits, but each fused as per OEM.

[EagleMark]

For humor: My wife got really frustrated when an intermittent short popped the ecm fuse in her '90 Sunbird on her way to work one day. She used every fuse in the 100 fuse assortment I'd placed in the trunk trying to make the car go. The original fuse was either 2 1/2 or 5A and she used everything in the box including all the lower amperage fuses then working up to (10) 20A fuses, (10) 25A, andn (10) 30A before giving up. When I got to the car it was easy to find the short. All I had to do was follow the one copper wire that had huge bare spots interspersed with melted pink insulation from the fuse panel, under the dash, past the instrument cluster, through the bulkhead connector in the firewall, through the starter and ignition harness to the back of the block. There were probably 15 other wires that had been damaged as well. I ended up getting a used harness and replacing the engine and dash sections rather than try and replace sections of all those other wires.

Lucky she didn't know about tin foil...

[dyeager535]

Going to hijack my own post. Can anyone tell me what the unused cavity plugs for the 1227727 connectors "are"? Based on the cable seal part number given here http://www.thirdgen.org/techboard/po...535-post4.html Mouser comes up with this http://www.mouser.com/Search/Product...Jex%2FKw%3D%3D But I don't see what the "number" of the terminal is. I'm sure it's either 100 or 150, but I can't find anything that says for certain.

This http://www.mouser.com/Search/Product...wkglpGuQ%3d%3d is the same style unused cavity plug as the ones that I have already, I'm just not sure if there are different sized plugs. I need almost 50 of them, so I'd hate to buy that many to find out they are the wrong ones.

[belaw]

I may be able to help on this one! The standard ECM/PCM terminal and connector is the MicroPack 100. I assume the '7727 uses the weatherproof equivalent 100W terminals, so I believe what you need is the MicroPack 100W seal / cavity plug:

http://www.eficonnection.com/eficonn...spx?ItemId=286