1972 620 + KA24DET = New Project

[maximumunicorn]

Hi folks. I only learned about this forum maybe a week ago when this truck popped up on (relatively) local craigslist.  I put up an initial post in the 620 sub-forum, but I thought it'd be nice to have a build thread.  If nothing else, it's a nice repository for my goals and aspirations regarding the truck.  So here's the basics:

 

Someone had performed the physical swap, then the next owner made it another chunk of the way.  Still doesn't run.  I picked it up recently with a friend of mine in Maine and I'm hoping to finish it up and take it out on the road.  A picture, because I understand the frustration when there aren't any:

 

 

Some more details:

1. It's got the can/am relay setup, so theoretically wiring should be simple.  That being said, the wiring harness has more exposed wire and butt connectors than I've ever seen, so tracking down specific issues is going to take some patience.  

 

2. It does crank now, but it's not getting any spark.  Making sure that power is getting to the ECU and can/am box is probably my first point of attack.

 

3. I've got all the fixin's on the way for a new fuel system (cell, lines, fittings, pump, filter) and a couple odds and ends to complete the turbo setup.  At least to a point where we can try to get it to run.  Both the fuel pump and electric fan will have dedicated switches.

 

Crappy engine picture:

 

 

The first owner definitely made some very strange decisions and it'll be a long process (especially since I'll only be able to put in a couple nights a week), but I'm real happy with the truck and I look forward to sharing and absorbing knowledge with the Ratsun community.

 

And yeah, more pictures to come.  If you want to see anything specific let me know and I'll try to grab a shot.  

 

That's all for now!

 

-Brendan

[datzenmike]

The fan should be automatic. Switches are subject to human error. The KS (some at least) like in the S13 used an in-line sensor in the rad return hose.

[orangie]

You're running into the same problem as I am with an SR20det.  The exhaust is going to cook that master cylinder.    I would wrap the exhaust if you can fit it.  BTW, I like your combination.

[maximumunicorn]

Good point on the fan.  I've got plenty of human error.  

 

orangie, thanks for the tip.  A fair amount of that setup is going to be redone before it's driven.  One of the strange decisions the first owner made was welding the (eBay) turbo directly to the manifold "to prevent leaks."  The downpipe itself is hacked together.  My friend who's helping with this owns a shop so we'll probably coordinate to build a custom downpipe/exhaust.  

 

First I've got to track down the power/spark issue, make sure fuel is getting to it, and get it to run!

[maximumunicorn]

Alright, one step closer.  Last night I sorted through some of the wiring and got the light on the ecu and two of the three lights on the can/am box to light up ('fuel pump ok' light not illuminated).  Still cranking, no spark.  Then I went to the ignition coil to see if that's functioning properly.  The power going to it, which I think is the black/red wire, is getting the full 12v so I'm not sure what the next step would be in diagnosing the lack of spark.  I just found the FSM, so I guess I'll do some reading and try to test the coil and distributor based on manufacturer recommendations.

 

I read somewhere that it won't spark if the fuel pump is not energized.  Is there any truth to that? Do I need to make sure that third light on the can/am box illuminated and the fuel pump is priming before I check spark?

 

Oh, and because I like putting the cart before the horse, some bits started arriving yesterday.  Purple adds horsepower, correct?

[UnderControl]

Tial Q, nice.

[dukerollo]

Your user name made me giggle. Welcome to the forum. My wagon has purple seatbelts, so it is pretty much a Race car.

[datson4life]

Ka hates weak grounds, also coil? Or dizzy not timed properly will not let ka start

[maximumunicorn]

Thanks for the comments and suggestions.  

 

I did some testing per the FSM and figured out that the Ignition Control Module (called Power Transistor in the FSM) is not functioning properly.  So I'll try a new one of those and see if that solves the problem.  The resistor/condenser may be an issue as well.  But the wiring itself tests right.  

 

datson4life, grounds are good and dizzy is timed properly.  Glad I checked though; I found some funky wiring that'll need to be cleaned up at some point.  

 

We also pulled the bed/fuel tank off in anticipation of mounting the new cell and lines.  

 

Oh, and if the whole lowered/drift truck build doesn't pan out for some reason, we could always go the opposite direction and lift it for 35s...

 

[Charlie69]

Fuel pump has to have power or no spark.

[maximumunicorn]

Fuel pump has to have power or no spark.

Thanks.  Exactly what I needed to know.  I'll be running an aftermarket fuel cell, lines, filter, and pump wired on a separate circuit.  Can I just ground the pump relay wire from the ecu (black/pink from what I can tell looking at wiring diagrams) to trick it into thinking there's power going to the pump? 

 

Sorry if this is a silly question; I've been looking at wiring diagrams for a bit too long this evening.  

[maximumunicorn]

Lots of updating to do after today.  First, and most importantly, it runs! (poorly)

 

There were a few things at fault preventing it from running.  I swear, the deeper I get into this project, the less I understand about the original owner.  Why were decisions made the way they were?  It's just awful so often.  I guess this is why buying someone else's basket case is usually more difficult than just swapping an engine start to finish.

 

1. Fuel lines hooked up backwards.  

2. Black/white wire from the crank position sensor plug was grounded for some strange reason (not getting 12v as it should).

3. Ignition control module (power transistor for those reading along with the FSM) was bad.  Got a new one at Autozone.

 

So after those items got sorted out in their unique, roundabout ways we actually fired it up and got it to sputter and stall.  It'll run under throttle, but it's super, super rich.  To my knowledge the ECU was never tuned for any sort of forced injection and I really think it has no idea what's going on with the combination of a high flow N60 MAF and 550 injectors.  

 

I was reading somewhere that the N60 combined with 370s actually balance each other out a bit and it can run without a tune (it must be true; I read it on the internet!).  I know, I know, that's just a patch at best.  But! I don't plan on doing that.  My next step is figuring out what to do about engine management keeping in mind that my existing wiring harness is pretty much toast.  As far as I can tell my options are as follows:

 

1. Send the ECU off to get a tune.  Maybe replace harness also.  

2. Buy a standalone system.  Wire it proper with the bare necessities.  

 

Although more expensive, option 2 seems more likely at this point.  If I were to make any changes in the future it'd be nice to be able to tune/adjust for them.  If you've read this far, do you have any thoughts on the subject of standalone engine management, KA24DETs, and 620s?

 

And because people like pictures, here's a picture in poor lighting with the bed and hood off.  In surgery as it were.

 

 

 

[UnderControl]

I'll likely be going stand alone when adding boost. There are other options including but not limited to nistune which allow for full tuning capability on a stock ecu.

[maximumunicorn]

I'll likely be going stand alone when adding boost. There are other options including but not limited to nistune which allow for full tuning capability on a stock ecu.

Thanks.  Certainly good to know about options.  I've probably got a couple weeks before I make a decision, so reading is in order for the time being.  

[maximumunicorn]

I picked up something while my engine management planning develops:

 

 

Since basically the entirety of the 620 suspension will need to be replaced and/or rebuilt I figured this was as good a time as any to find an s13 rolling chassis and pull subframes and anything else useful.  Picked this one up yesterday with a friend of mine (you may recognize the truck/trailer from the original post), pulled everything we wanted last night, and the rest is going to scrap this morning.  Should be fun.

[Lockleaf]

Are you familiar with the Project Car Magazine 620 build? They install s13 suspension under a 620 as well. It covers, in pretty good detail, building the strut towers, fitting the subframes, pretty much all of it.

[maximumunicorn]

Are you familiar with the Project Car Magazine 620 build? They install s13 suspension under a 620 as well. It covers, in pretty good detail, building the strut towers, fitting the subframes, pretty much all of it.

I'm not familiar with that build.  I'll have to hunt for it online.  I wonder if I can find some back issues.