I posted this in my other thread and got absolutely nothing. I PM'ed HowieE about it, and again, nothing. So now it has it's own post...

I have reread HowieE's write up about wiringing in a relay to releive the ammount of current the OPS carries. I wasnt sure I understood it properly, so I redrew the diagrams with how I think it works.

Are these both correct?

here is the OEM wiring:

http://www.fotothing.com/photos/750/750bd30ebbfea6a52f703ea6bcc274da.jpg


and here is how it should be wired with a relay?

http://www.fotothing.com/photos/85e/85e36ddb7b3eb2778b429f4e267d5b8a.jpg

I can't help you, i've never done it. I have 2 or 3 relay's in the garage that are new, me and electrical power aren't very good friends. I can just fumble my way around a bit.

ttt - someone has got to know, and I want to know for certain before I strip the first wire....

I'm by no means an electrical expert. But by looking at the first diagram, the ops and the lift pump are wired in parralel, not in series. I don't see how the ops can shut down the lift pump if there's a loss of oil pressure.

in the second diagram, they still appear to be in parrallel.

Is your question specific to the new relay, or to the existing system?

I'm going to bypass the ops pretty soon. I might wire the ops to an alarm incase it ever does lose oil pressure. I'm interested to know what you figure out with this.

Do you have a link for the original thread?

I'm by no means an electrical expert. But by looking at the first diagram, the ops and the lift pump are wired in parralel, not in series. I don't see how the ops can shut down the lift pump if there's a loss of oil pressure.

in the second diagram, they still appear to be in parrallel.

Is your question specific to the new relay, or to the existing system?

I'm going to bypass the ops pretty soon. I might wire the ops to an alarm incase it ever does lose oil pressure. I'm interested to know what you figure out with this.

Do you have a link for the original thread?


That's odd because in Howie's page he has them parallel like in mine. The fuel pump relay switch is only shut when the glow plugs cycle. After the glow plugs shut down, the fuel pump relay switch stays open leaving only the OPS to supply voltage to the lift pump. Basically I want to incorporate a 40amp relay to take the current load off of the OPS and instead use the OPS to trip the relay. This way the OPS only conducts about 0.25amp vs its usual 5-8amps.

Here is the origional thread:

http://dieselplace.com/forum/showthread.php?t=84660&page=2

and here is howie's diagram (hope you dont mind howie) the black lines are where the relay is incorporated:
http://mysite.verizon.net/vze54tx9/sitebuildercontent/sitebuilderpictures/ops.jpg

here is Howie's site that that came from:
http://mysite.verizon.net/vze54tx9/id13.html


does anyone have any OEM wiring schematics for the lift pump, ops, and fuel pump relay circuit?

It just got answered! Props to Howie for coming to the rescue! Thanks guys! :)

now I'm confused.:confused: The lift pump has two separate power sources? The lift pump relay and the OPS?

Does the factory relay constantly give power to the lift pump, or only when the ignition is first keyed "on"?...maybe I figured it out.:confused:

now I'm confused.:confused: The lift pump has two separate power sources? The lift pump relay and the OPS?

Does the factory relay constantly give power to the lift pump, or only when the ignition is first keyed "on"?...maybe I figured it out.:confused:

Yes they both independantly are capable of supplying power to the lift pump. That relay labeled "fuel pump relay" is only on and giving voltage to the lift pump when the glow plugs are on. Once the glow plugs turn off so does it. The lift pump is then returned back on again by the OPS when oil pressure is up. At least that was and is my understanding of it. Hope that helps. :)

yes, that definitely helps. :) thankyou!

So did Howie say you were correct with your diagram with the added relay?

The OPS supplys power to the lift pump only when the engine is running, the fuel pump relay on the 94-95's only supplys power to the pump when the starter is engaged(not the glow plugs). If you run a wire from the glow plug relay output to pin 87A and reverse the connections between 87 and 30(30 should be the hot wire [99.9% certain on this one:o:]) this will power the pump during glow plug operation and not feedback through the system.

This becomes a nice reference thread with the shematics/sketches, Bumpin. I think Ferminator is cirrect about '94 + '95 model yrs, and Bumpin/Howie's description holds for later models. I'm pretty sure that 95 has a diode in lines to prevent backfeeding....

I don't remember the terminal numbering [unless i'm actively wiring], allow me to add the following sites which list/illustrate the standard Bosch automotive relay wiring/numbering:

-Relay action, numbering, wiring, and 'back-EMF' protective diode installation wiring/config: http://www.bcae1.com/relays.htm

-Bosch wiring numbering:
http://www.190slgroup.com/tech/images3/bosch-terminal1.html

-Other entries for relay number/wire:
http://www.rowand.net/Shop/Tech/images/RelayWiringGuide.jpg

http://sw-em.com/lighting.htm

http://www.stealth316.com/2-fuelpump-rewire.htm

The OPS supplys power to the lift pump only when the engine is running, the fuel pump relay on the 94-95's only supplys power to the pump when the starter is engaged(not the glow plugs). If you run a wire from the glow plug relay output to pin 87A and reverse the connections between 87 and 30(30 should be the hot wire [99.9% certain on this one]) this will power the pump during glow plug operation and not feedback through the system.

You mean if I did this?:

http://www.fotothing.com/photos/8ab/8abcb0d0953afeb36f83c109cd8b2cb8.jpg

My main goal of releiving the OPS of its current has been accomplished, now here's an interesting question....is it desirable to have the lift pump kick on when the glow plugs kick are on as well as during crank?

Steve

ps - I really really dont want to come across the wrong way but I did wanna say one thing...The 30 vs 87 for input voltage doesnt matter, http://www.the12volt.com/relays/page2.asp Check out the starter kills. Notice the 12v from the ignition enters in on either 87 or 87a pending normally open or normally closed setups. :) But yes the norm is hot into 30, but its not a huge biggie. :)

Connect the grey wire to the lift pump to pin 30
Connect pre OPS orange wire to pin 87 ( normaly open )
Connect +12V output of Glowplug relay to pin 87A ( normaly closed )

Rationalization
Ignition switch to run, glow plug relay is energised as needed, lift pump is powered by glow plug relay through normaly closed contact of new OPS relay. Glow Plug relay opens, lift pump off
Ignition switch to crank, fuel pump relay is energised, lift pump is powered by fuel pump relay. Combustion
Ignition switch to run, fuel pump relay off, lift pump off.
Oil pressure closes OPS, new OPS relay is energised, lift pump is powered by OPS relay.

Diodes as required to prevent feedback

Connect the grey wire to the lift pump to pin 30
Connect pre OPS orange wire to pin 87 ( normaly open )
Connect +12V output of Glowplug relay to pin 87A ( normaly closed )

Rationalization
Ignition switch to run, glow plug relay is energised as needed, lift pump is powered by glow plug relay through normaly closed contact of new OPS relay. Glow Plug relay opens, lift pump off
Ignition switch to crank, fuel pump relay is energised, lift pump is powered by fuel pump relay. Combustion
Ignition switch to run, fuel pump relay off, lift pump off.
Oil pressure closes OPS, new OPS relay is energised, lift pump is powered by OPS relay.

Diodes as required to prevent feedback
What he said, I went and double checked and was incorrect about the swapping(really tired last night, hence why I was only 99.9% certain). You can get a 6 amp relay from radio shack that should do the job to prevent feed back to the glows as well. I used a FORD starter solonoid on my glows to power them and used the I terminal on it to power the lift pump during glow operation.

Here is how I did mine, I connected my momentary switch up to the S terminal as well for manual operation. Has worked without DTC's for a year and a half now. It didn't come out very well, but basically I use the FORD solonoid to carry the load and the origanal just to switch the FORD one for auto operation.

Question: on the 96 and newer vehicles is the lift pump energised during ignition start or only during the glow plug cycle?

I see in my 95 service manual that the OPS should close at 4 psi. This would close the OPS lift pump circut quickly at ignition start and then energise the lift pump until oil pressure drops below 4 psi.

iirc the computer runs the 96 and newer lift pump until the ops takes over, after start .

Lets see if I can attach these pics right

Stock lift pump circut
21771

Stock glow plug circut
21772

Modified lift pump circut
21769

Modified glow plug circut
21770

Lets here some feedback, also I need better knowledge about diodes.

wow impressive!

That should work!

Diodes prevent flow of current from one direction. IIRC current can flow from annode to cathode, but not cathode to anode. The striped end of the diode is the cathode. We used to use the damn things all the time in car alarm installs. ugg. lol

I realize you want to install the relay to reduce the amperage travelling through the ops. I do not know why and I am not being sarcastic. Does the OPS create a resistance that may slow the pump down or is there a reason I am missing?

Here is how I did mine, I connected my momentary switch up to the S terminal as well for manual operation. Has worked without DTC's for a year and a half now. It didn't come out very well, but basically I use the FORD solonoid to carry the load and the origanal just to switch the FORD one for auto operation.

Could you redraw that in mspaint? I'm lost as to what you did but I have essentially the same system but get the GP DTC every startup.

I realize you want to install the relay to reduce the amperage travelling through the ops. I do not know why and I am not being sarcastic. Does the OPS create a resistance that may slow the pump down or is there a reason I am missing?
The OPS is a common failure item causing slow fuel to the IP. The OPS has contacts rated at 1 amp and the lift pump is drawing 4 amps. Failure is routine.

I realize you want to install the relay to reduce the amperage travelling through the ops. I do not know why and I am not being sarcastic. Does the OPS create a resistance that may slow the pump down or is there a reason I am missing?

lol exaclty as QM said. over time the contact corrode in the OPS and next thing you know the lift pump no worky. (In my case if I unplugged the lift pump and measured voltage I'd get 13.8 going into the LP in the gray wire. But the moment I plugged it in the gray wire dropped to less than 8v!) I JUST replaced both the OPS and the fuel pump relay (the fuel pump's relay was corroded too) and everything is working like a charm and Id like to keep it that way!

Is that your 50BMG? I want one so damn bad! aarrg

Is that your 50BMG? I want one so damn bad! aarrg

Yep. Steyr Mannlicher 50HS (heavy sniper) with Nightforce 8-32 x 56 on top. I am not that good with it yet but I can nail a 6" plate at 500 yards every shot now. The long range shooting with target turrets is way different than the old hunting rifle. I get lucky at 1000 yards every once in a while and I hope to be shooting a full mile by next fall. I am taking it Elk hunting this fall. There is nothing but wheat fields and prairie grass up here so it is alot of fun.

QM I used MS paint but I can see it turned out grainy. I will try to improve.
When you click on the thumnails and open the attachment, is the orignal photo readable but the red changes not?
Can you describe your setup?
What code are you setting?

Bumpin' do I understand correctly that a diode can be used in line? In TomMac's references I only saw a diode used in parallel on a relay coil to quench reverse voltage.
I am thinking about a different wiring plan, do you think the lift pump needs to be energised during ignition start (crank)? The OPS will close at 4 psi, how many seconds would that take?

Jason 94 & 95 only power lift pump on ignition start and when OPS sees 4psi oil pressure. 96 & up power lift pump on glow plug cycle and when OPS sees 4 psi, possibly also on ignition start. Most people think it is better to pressurize the fuel system before ignition start.
Could you check the lift pump on your 96? Pump should be on when glow plugs are on then off. Does pump run again at the start of cranking starter or run at closure of OPS? I have checked mine by touching pump with one hand and turning key switch with other.

I think mine is functioning properly. I was just curious. When I turn the key on I hear the pump easily before I start to crank. It has an SS Diesel pump on it now and it is quite audible. I know it turns on and off with the glow plug cycle. I do not hear it after the glow plugs turn off and before I crank the engine. I can hear it running while the truck is idling and after I shut the truck off too - it is probably running until the oil pressure is gone. I am not sure if I can reach the key and the pump at the same time. You must be a big dude. Just my belly is big and it is getting in the way. If I can not reach it I will get somebody to crank it for me so I can check it out.

QM I used MS paint but I can see it turned out grainy. I will try to improve.
When you click on the thumnails and open the attachment, is the orignal photo readable but the red changes not?
Can you describe your setup?
What code are you setting?

. I'm getting the GP code. My set up is a ford starter solenoid with a momentary switch wired into the pink/blk ignition wire to the switch. You press the button and you get glows but DTC comes at key on for the GP everytime.

I'm getting the GP code. My set up is a ford starter solenoid with a momentary switch wired into the pink/blk ignition wire to the switch. You press the button and you get glows but DTC comes at key on for the GP everytime.

DTC 29 ?
Glow Plug Relay Circuit Fault
Will set when
Glow Plugs commanded ON and Glow Plug volts is less than .8 volts
or
Glow Plugs OFF and Glow Plug volts is greater than .8 volt
or
System voltage exceeds Glow Plug volts by 2 volts


I assume you do not like the factory Glow Plug cycle and want manual control, or your relay died and the Ford was the fix. The PCM controls the glow plug relay and expects a signal back. You could go back to the factory system or we can fool the PCM. What do you want to do?

fool the PCM of course, the other thing I didn't mention is that I have the lift pump on a 30A accessory relay but it is switched by the ignition, not the OPS.
Would adding the wire and diode to pin 87a form the starter relay cure the code?

QM
DTC 29
Glow Plug Relay Circuit Fault
Will set when
Glow Plugs commanded ON and Glow Plug volts is less than .8 volts
or
Glow Plugs OFF and Glow Plug volts is greater than .8 volt

Both of these conditions are a problem for your setup. Assuming 94 and 95 wiring is the same, I will look up the the wiring and pinouts for a jumper at the PCM. Lift pump operation is unaffected until we complete the lift pump on at glow plug cycle modification. For safety you should consider going back to the OPS control when we finish this mod.

You guys have me lost but i have a little bit to contribute here i think.

On my OBDII the GP code will only show up if you apply voltage to the circuit while the ECM is also commanding the GP's on. I used to throw GP codes all the time with my Penninsular timing control added on so i got rid of it.

All i did was wire a hot wire from the batts to a 50 amp dash switch (60 amp breakers in between) and then out to the GP side of the controler. When i do the key on i simply wait for the ECM to finish its on/off cycling (about 30 seconds) and then flip my switch to power the GP's, haven't thrown a code since.

CR: Sounds like OBDII only checks glow plug volts during ON cycle.
My 95 service manual says DTC 29 will set if glow plug volts is more than .8 volts during OFF cycle. From QM's Posts I dont think he is using the stock glow plug relay just his manualy switched Ferd relay. I am thinking a jumper from stock glow plug relay power to glow plug volts sense will fool the PCM with what it wants to see.

CR: Sounds like OBDII only checks glow plug volts during ON cycle.
My 95 service manual says DTC 29 will set if glow plug volts is more than .8 volts during OFF cycle. From QM's Posts I dont think he is using the stock glow plug relay just his manualy switched Ferd relay. I am thinking a jumper from stock glow plug relay power to glow plug volts sense will fool the PCM with what it wants to see.

I think "cycle" might be the key word. Once its done its "cycling" maybe it no longer checks for voltage there?

I would see if OBDI works the same as II but i'm not anywhere near my Blazer.

I'm running this setup on my '94 (no engine or tranny at this moment) and the '96, so I need to think about both systems.

Desert Rob
>Bumpin' do I understand correctly that a diode can be used in line?
Absolutely, provided it is/has adequate current capacity to carry load, and enough voltage insensitivity to withstand its' environment.
SEE: http://ourworld.compuserve.com/homepages/g_knott/elect212.htm
ALSO- http://ourworld.compuserve.com/homepages/g_knott/elect216.htm
There are lots of diodes in the OEM harness.