Hi folks. Ok, five years and the piles of parts have actually gone back onto the car. And, I er, ah tightened the head nuts to the proper torque. My problem is that it is hard to keep the motor running long enough to tune it. For example timing light.

The problem is that I want to adjust timing and fuel, but The motor isn’t running smooth enough to get there. The motor is a 2056 with the so-called Raby cam from WebCam. The MPS has been messed with, but it ran when parked. Took the motor out to split the case and address oil leaks. One thing led to another and the rust was replaced with yet to rust sheet metal, and paint etc.

I am looking for a starting condition that allows enough running to improve upon. Ideally, I would like the motor to idle somehow. I have a pretty big hint. If before start, with ign on I blip the throttle a few times, the fuel injectors click, and the motor will start, run and die. From this I think that the sparks are there and the injectors are capable of letting out enough gas to fire. The fuel pressure is constant 29 psi, and the injectors have been cleaned and tested. My problem is the MPS and ECU black boxes that govern fueling. I have an AFR gauge, but it would be more useful if the motor ran long enough to get a number to look at.

I am hoping for:
A magic bullet post that says something like clock the seatbelt bolts and it will start,

Or, basic starting adjustments for each thing that can be adjusted or tested. For example, I can static test the timing and measure MPS inductance vs vacuum. What else has to be in line? Head temp resistance value? Throttle TPS switch position or values? You folks comprise so much wisdom, so please let me get the car on the road now that spring is only months away!

You can have an incredibly badly tuned mps and the car will idle. I often forget to plug the vacuum line into mine when I am mucking around and end up driving it around the block like that.

I think you have a fundamental issue here. Can you keep it running by blipping the throttle or is that only for a short time?

Can keep it going by throttle. Wondering if something like dizzy or cam timing is off. But then that is the fear that sends me here.

Sounds like fuel delivery to me. Head temp sensor connected? What is the resistance on it? Don't worry about mps and ECU yet. It seems that you can fire the injectors using the TPS. Do you still have the original distributor? Are your trigger points hooked up and are they working?

What is the "So called Raby cam from WebCam"? Could you be more specific?

Djet needs a really mild cam to run - preferably a stock grind. Raby did optimize a camshaft for Djet - the MPS needs to be tuned for it. And I don't think you can buy that camshaft from Web Cams. You need to buy them from the Type4store.com.

So what cam are you using, exactly. And what have you done with your MPS, exactly.

Thanks
Zach

@worn

Can you elaborate on how you keep it running with the throttle?

Are you keeping the throttle at a constant position?

Are you continually blipping the throttle to keep it going?

From your initial post, you wrote:

If before start, with ign on I blip the throttle a few times, the fuel injectors click, and the motor will start, run and die.

If the trigger contacts in the distributor were not functioning, you would have this result. Moving the throttle causes the injectors to fire as they mimic the accelerator pump in carbs. However the injectors are fired only when the engine is turning and the trigger contacts are functional. The firing of spark plugs is totally independent of the FI operation.

Smart idea. But I am just opening the throttle to keep the revs up. Not pumping. Seems to be one of those runs only when cold things

Before jumping down the rabbit hole and making more changes, let's get a baseline.

-Dan

How long can you keep it running, and by running do you mean 'good' or on the edge of not running?

I am not a huge fan of worrying about the MPS and such at this point. The CHT and timing are far more impactful than the MPS for this early stuff. You could have a blown diaphragm and a disconnected vacuum hose and that MPS will still let your car run. Pig rich, but running.

Now, cam might be a thing but we have ways of cheating that for troubleshooting. Do you have a vacuum gauge or pump with a gauge you can stick on your plenum?

And you still need to let us know if you have the stock distributor.

Update. Checked the CHT sensor by measuring resistance and substitution. In my hands the resistance is about 3-4 Kohl’s (apparently a new spelling version of kilo Ohm) at a cool sixty degrees f. No help there. Resistance looked good and decreased with warmth. New sensor did the same and didn’t help when substituted.

The situation seems to be getting worse. Now I find that most of the time no fuel comes from the injectors. I am looking at #1 and #2. Occasionally the car will cough and that is associated with the injectors firing. Fuel pressure is at 29 psi, and when I hook the injectors up to a cheap little test box they squirt just fine off of residual pressure.

On to the trigger points. Checked the trigger points with an ohm multimeter, and they open and close as the rotor is turned, one side 180 degrees apart from the other. I then connected a different spare distributor to the harness and turned the rotor with the ignition on. As I turn the rotor the fuel pump cycles on and off but the injectors don’t fire.

At this point I am wondering about the CPU. Any other ideas? I am trying now to wade through the wonderful documents compiled by Brad Andre’s to understand the link between ecu and the fuel pump. Also looking into what part of the system drives the injectors. The parts have been kept dry, but they certainly have been heat and cold cycled.

So - again. Your MPS is going to determine your fuel load.
It sounds like you are not using a stock cam grind.
Have you adjusted your MPS for the cam you are using? Is your cam suitable for djet?

What color are your spark plugs? Are they shiny and black? Are the gumming up?

Zach

I don't know Zach, the mps just isn't that sensitive. You can have it way off and the injectors will fire, just not much or too much.

If you want to test the mps, just pull the vacuum hose off of it. That will tell the ECU to go pig rich (wot).

If the cam were the problem we would have too much fuel due to low vacuum at idle.

I couldnt tell from your write up, but did you spin the dizzy with the key on out of the car? Just to see if the injectors are firing when the points tell them to?

Could be a wiring issue too, how old is the harness? Original?

ECU can't be excluded as the culprit at this point of course. Any extras laying around?

Did you do a leak down test on the mps? Check the resistance? And of course triple check the plugs wire order?

Thanks for the help everyone. This is the cam card. I believe that it was Rich Towle who suggested it, but it was quite some time ago. I rebuilt the motor because of excess smoke from rings and valves and added this web cam order.
Click to view attachment
Note: I ran the car and autocrossed it for a couple of years with this cam. And yes, I had to tweak the MPS and buy and use an inductance meter and A/F gauge and monitor head temps. It leaked oil though, and with the motor out I found that the body needed a lot of repair. So, this is the awakening of a motor rebuilt to fix oil leaks and set aside for 4 years.

I hope that settles the cam part. Also, the motor has run recently. But it seems to be less and less willing to start.

Interesting, so definitely run diagnostics on the MPS and verify the injectors are firing at the command of the trigger points. That should lead you to the next step. Did you put a new harness on it?

I have a spare MPS, calibrated acording to Brad Andfdrs excellent write up. That made no difference.
The cam ran well several years ago, for road and autocross. I put at least 5,000 miles on it.

I finally pulled out the injectors for #1 and #2. Asked them to squirt in a cup. No fuel coming out when cranking. Fuel pressure is at 29 psi, and the injectors spray perfectly when stimulated by a cheap little amazon injector driver. Nice tool incidentally.

Pulled the trigger points and they look fine and function on the bench. However, just to be sure I connected another dizzy to the trigger connector and spun the rotor with the ignition on. That produced no response from either injector, but it did cause the fuel pump to go on and off as I turned the shaft. THat has me puzzled because I cannot trace the wiring for that.

I tested the resistance of the head temp sensor and it was 3-4 kilo Ohms, and I also substituted a new sensor with no success.

Finally, I have messed with the harness. I put new connectors and boots on the engine harness. In addition, I disassembled the block that plugs into the relay board to get the wires through the snorkel. With those caveats in mind, I was very careful, and the motor has run for several minutes, but would not restart after warming. Now it doesn't seem to want to start at all.

I have a couple of old ECUs that I can try, but that has seemed a long shot toi me so I haven't. Anything else before I try that? I hate to strain the boards with that big plug.

Thanks again!

wow, that really does make me wonder about the ECU. It really isn't bad to unplug so if you have extras I would give it a go, easy, quick. And do a quick leakdown test on that mps just in case.


what year is the car/ecu?

have you tried running it with the tps disconnected?

I did a leak down when I double checked the MPS inductance values. Gonna recheck though.

It is a '76.

Thanks. I will try swapping the ECU. Wish I remembered the history of the spares better, as in known good or not. Bought on eBay just in case years ago.

Do try running it with the TPS disconnected first.

Have tried day before yesterday and will try again. Thanks!