Problems installing DUI Distributor from Performance Distributors

[1984]

Hello all. First post to the forum although I've lurked a bit since I got my 89 Nissan. VG30 engine with a Weber carb.

 

So yesterday I installed a DUI Distributor. The truck starts up and runs smoothly but for whatever reason the fuel pump doesn't turn on. It'll turn on for 5 seconds when I turn the ignition to the on position but once this fuel get used it runs out of gas.

 

Here's my theory: Since the camshaft position sensor (CPS?) was in the stock distributor the ECU is no longer receiving a signal that the truck is running.

 

I tested this theory by hooking the CPS wires up to the tach output on the DUI Distributor. Low and behold the fuel pump runs but the truck won't turn off. Or I should say that the key will turn the fuel pump off and the truck will run out of gas. I should note that the CPS wires have 5v when the ignition is on.

 

I've talked to Performance Distributors several times today and they've never seen this problem before. Am I the first person to install a DUI distributor on a Nissan D21 with a VG30?

 

Can anyone provide any insight to this scenario? The simplest solution that I can think of would be to put a one way diode between the tach output and CPS wires. This way the CPS gets the tach signal to fool the ECM but the distributor isn't getting the 5v.

 

Any help would be greatly appreciated.

[datzenmike]

The 'distributor' (has rotor and cap with plug wires) is known as a CAS for Crank Angle Sensor. It lets the ECU know exactly where the crankshaft is to one degree.

 

Why are you changing it? There's a disc with 360 marks on it and four others spaced 60 degrees apart, a light source and a photo-electric cel to 'read' the marks. Not much to wear out.

[1984]

Changing it to get advanced timing for the Weber carb. I honestly thought the new dui distributor had vacuum advance as well as the mechanical advance. 

 

Mostly was hoping for better gas mileage and the possibility of more power. 

 

The ECU gave code 11: crank angle sensor/camshaft position sensor.

 

The DUI Distributor was supposed to be a straight forward install for the VG30. Give it full volts from the battery/alt and it will go. The company employees are baffled and plan to talk to the owner on Monday.

 

And I'll note that two days ago I knew nothing about distributors and timing and... Figuring it out as I go. Thanks for the response.

 

 

 

[1984]

Oh and maybe I should note that the DUI Distributor has two wire hookups: tach and batt

[datzenmike]

So getting rid of the CAS and putting in an actual distributor then.

[1984]

Yes, I suppose, but what is the best way to get rid of the CAS in this scenario?  I was under the impression that the distributor contained the CAS. Still a distributor but also has the CAS.

 

What is the most logical/safest way to make this work? 

 

Like I said, I don't know much about this besides a couple days research.  

 

My thought was to connect a CAS wire to the distributor tach output so it gets the 'engine running' signal but put a diode in the line to cut off the voltage that the CAS would be sending to the distributor, preventing it from shutting down. Does this make sense? Any harm in doing this?

 

I drove the truck for 30-40 miles tonight with the CAS connect to the tach output on the distributor like this minus the diode. It ran great. Was able to adjust the advance and tune the carb. The only thing is that the ignition will only turn off the fuel pump so it doesn't shut off right away. It has to run the carb bowl out of gas. One thing I noticed in doing this was that the fuel pump regulator had to be opened up to allow more pressure as if the fuel pump wasn't pumping at it's regular rate.

 

I could also wire the fuel pump so it's not triggered by the CAS via ECU. (Not sure if this is actually what happens or if it would work). Could the fuel pump be wired to the ignition?

 

 

 

 

 

 

[Skib]

8 minutes ago, 1984 said:

 

I could also wire the fuel pump so it's not triggered by the CAS via ECU. (Not sure if this is actually what happens or if it would work). Could the fuel pump be wired to the ignition?

 

 

 

Yeah you could just change the power input on the relay to a keyed 12v source.

 

You have switched to a carb and are running a non ECU controlled dizzy.... so what else is the old ECU actually controlling?

[1984]

5 minutes ago, Skib said:

 

Yeah you could just change the power input on the relay to a keyed 12v source.

 

You have switched to a carb and are running a non ECU controlled dizzy.... so what else is the old ECU actually controlling?

Besides the fuel?  Not sure. Some instrument cluster stuff? I really don't know but I do know of one way to find out.

 

I tried to unplug the ECU this morning just to see what happened but I couldn't get to the wire harness without taking out the seat

[Skib]

4 minutes ago, 1984 said:

Besides the fuel?  Not sure. Some instrument cluster stuff? I really don't know but I do know of one way to find out.

 

I tried to unplug the ECU this morning just to see what happened but I couldn't get to the wire harness without taking out the seat

 

 

The ECU has inputs, I don't think its running to many outputs sans fuel and spark. The CAS trigger wheel only has 6 slots and runs the fuel injectors. 

The gauges should all be independent of the ECU. In the 90s when Nissan changed to things like speed sensors they added a lot more ECU dependent stuff.

Its been a few years since I was elbow deep in a VG30

[datzenmike]

The ECU did control the automatic shift points to some degree. It set the EFI mixture and adjusted the spark advance. That should be about it. If this was a KA engine an L20B distributor would work. The VG30 engines in Saudi Arabia were points if you could get one of those...? I recall an L28 matchbox distributor being turned down to fit a VG30.

 

The bottom line is this should work just run the pump as suggested from a switched ignition source.

[Skib]

Here is a PDF of the  factory service manual https://www.nicoclub.com/service-manual?fsm=Hardbody%2Fd21_truck_1989.pdf

 

 

 

[Skib]

Looks like pin 108 on the ECU is your control input to the fuel pump relay.

Just run that to a key on/cranking on power wire instead.

 

[1984]

3 minutes ago, Skib said:

Here is a PDF of the  factory service manual https://www.nicoclub.com/service-manual?fsm=Hardbody%2Fd21_truck_1989.pdf

 

 

 

Thanks! 

I'll look into connecting the pump to ignition power. 

[datzenmike]

You could also ground a relay through the oil pressure switch with the fuel pump connected to the NO (normally open) terminals. Pump is only on when there is oil pressure. In an accident, heaven forbid, when the engine stops so does the fuel pump.

[1984]

2 hours ago, datzenmike said:

You could also ground a relay through the oil pressure switch with the fuel pump connected to the NO (normally open) terminals. Pump is only on when there is oil pressure. In an accident, heaven forbid, when the engine stops so does the fuel pump.

Oh I like that idea. I think  I understand. 

 

The stock fuel pump relay is probably the wrong type eh?

 

Or could I remove the ECU wire from the relay and attach the relay ground to the oil pressure switch?

 

 

[1984]

Well now that I think about it it seems easier to put a diode on the CAS and connect it to the tach out on distributor. It will act as the safety switch for the pump. 

 

Any harm in doing this? The CAS worked with the old fuel injection which has been removed so it no longer does anything for engine performance? It's a 4wd.

 

Looking at the wiring diagram it appears that a bunch of stuff goes through the ECU so I don't think I'll remove it. 

 

What do you guys think? Diode?

[datzenmike]

54 minutes ago, 1984 said:

Well now that I think about it it seems easier to put a diode on the CAS and connect it to the tach out on distributor. It will act as the safety switch for the pump. 

 

Any harm in doing this? The CAS worked with the old fuel injection which has been removed so it no longer does anything for engine performance? It's a 4wd.

 

Looking at the wiring diagram it appears that a bunch of stuff goes through the ECU so I don't think I'll remove it. 

 

What do you guys think? Diode?

The tach output is a series of on off pulses across the coil. I don't think that would be good for the pump and if a relay it may chatter on and off.

 

 

The oil pressure sender is only at ground when the pressure drops below about 8 PSI and this turns the red oil light on in the dash. Many relays when off have a normally closed set of contacts and a normally open set.

 

 

The + is to the battery, the - to the oil pressure sender. When running and there is oil pressure there is no ground at the - terminal. The C and NC are connected to the fuel pump. When engine stops and pressure drops a ground condition at the - terminal energizes the coil and the NC connection is opened shutting the fuel pump off

[1984]

51 minutes ago, datzenmike said:

The tach output is a series of on off pulses across the coil. I don't think that would be good for the pump and if a relay it may chatter on and off.

 

 

The oil pressure sender is only at ground when the pressure drops below about 8 PSI and this turns the red oil light on in the dash. Many relays when off have a normally closed set of contacts and a normally open set.

 

 

The + is to the battery, the - to the oil pressure sender. When running and there is oil pressure there is no ground at the - terminal. The C and NC are connected to the fuel pump. When engine stops and pressure drops a ground condition at the - terminal energizes the coil and the NC connection is opened shutting the fuel pump off

Thanks for the info. I really appreciate you spending time to get the diagram and describe it. Thinking about relays is confusing for me since I've never really done it so this makes it easy.

 

But doesn't the CAS signal go to the ECU? And isn't a tach signal very close to what the CAS would normally be sending to the ECU? When the ECU receives the pulse from the CAS it knows the engine is running and switches on the fuel pump. Or am I thinking about this wrong? 

 

I'm not changing any of the wiring except for giving the CAS a pulsing signal from the distributor like it originally had. This pulse isn't making it to the fuel pump or relay is it? Wouldn't I hear the relay and/or pump pulsing if it were?

 

And I tried both the 1 degree and 120 degrees wires separate and together with the same result. I think the ECU just wants a signal from the CAS so it's telling itself it's running. 

[datzenmike]

I doubt is a 12v square wave. The CAS is just a photo electric cell 'reading' marks on a wheel. I don't imagine it's a strong voltage. I don't know. 

 

Simplest is a switched ignition source. My relay is just for safety.

[Skib]

The CAS is literally just for firing the fuel injectors. 

 

The only relative thing your ECU currently controls is sending power to the fuel pump relay, sort that and you don't need the ECU.

Don't over think the problem.

[1984]

Ok. Point taken. I appreciate the responses. I'll wire the pump through a safety relay.

 

But I do find it interesting that wiring the CAS to the tach enables the fuel pump. I already ordered a diode so I'll do an experiment. Plus I'm interested in what the distributor company has to say on Monday when they get back to me. Thanks again 

[Jesse C.]

On 10/28/2022 at 10:14 PM, datzenmike said:

The ECU did control the automatic shift points to some degree. It set the EFI mixture and adjusted the spark advance. That should be about it. If this was a KA engine an L20B distributor would work. The VG30 engines in Saudi Arabia were points if you could get one of those...? I recall an L28 matchbox distributor being turned down to fit a VG30.

 

The bottom line is this should work just run the pump as suggested from a switched ignition source.

 

The Saudi Dist. is a Magnetic Pick Up style, the stock VG unit is a HAL Effect unit. To my knowledge, there where not Point distributors for the VG. 

Some have used aftermarket point replacement sets to convert their stock VG dist. units. The only problem being no advance. 

 

Just in case, this is what the Saudi/NISMO distributor looks like. 

 

 

[1984]

10 hours ago, Jesse C. said:

 

The Saudi Dist. is a Magnetic Pick Up style, the stock VG unit is a HAL Effect unit. To my knowledge, there where not Point distributors for the VG. 

Some have used aftermarket point replacement sets to convert their stock VG dist. units. The only problem being no advance. 

 

Just in case, this is what the Saudi/NISMO distributor looks like. 

 

 

Looks pretty nice. Does the stock wiring harness plug into that? Is the CAS in there? 

 

The one I got from performance distributors didn't come with the vacuum advance as advertised. The picture on their site for the distributor has the vacuum advance but it's pointing the wrong way.

 

And also wasn't plug and play as advertised. Very expensive too.

 

Here's a link if anyone wants to have a look: https://performancedistributors.com/product/nissan-vg30-dui-distributor/

[datzenmike]

 

Looks like the GM odd fire six cylinder HEI distributor...

 

[Skib]

Hope you get it all sorted 👍