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turbogrill

Car wont start after rebuild - tips & tricks wanted

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Hi,

 

I have rebuilt our datsun L28 engine and now it won't start. I have changed everything from cam to electronics so could be anything. 

Last build I did was way more stockish and it started right up. It has the same setup but less aggressive cam and stock ignition.

 

It has Megasquirt for spark and fuel (Nippondenso cas with VW wasted spark towers) and a very aggresive cam.

 

Some observations:

- Fuel pressure. Fuel pressure goes down to 10psi during cranking (due to voltage drop to pump, about 8v)

- I have tested the injectors in megasquirt test mode (they are also just serviced)

- Using the timing light it's a bout 10 degrees when cranking

- Tried injector pulse widths between 5ms and 20ms during crank

- Disabled flood mode

 

It doesn't even make an attempt to start. It's exactly as if the ignition didn't work. I do get a little smell a fuel so I think the injectors are firing.

 

Any clues or tricks?

 

 

 

 

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Just now, Team Infiniti said:

10 psi is no good, if it does not try with starting fluid, suspect a electrical or mechanical timing issue.

 

Starting fluid! 

 

will try that!

 

My FPR bleeds of pressure really fast.

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Have you actually checked to see if you have spark?

If you have spark, and the starting fluid doesn't work, check compression.

 

If you have fuel, spark, and compression, check timing again.

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How is the health of the battery?   IIRC, I had issues with my MS3 on my Miata when battery voltage was too low.

 

 

Check that and re-charge if needed.

 

Then follow Rob's check-list.

 

 

Also, does the MS completely take out the entire stock EFI and ignition system?  I had issues with that one special dual relay thing on my EFI Datsun, swapping to a good one fixed a start issue (but I don't know if that part is still on your car)

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the internal combustion engine needs 3 things...air, fuel and ignition. Since you smell gas I'd check for spark. Have a teammate hold the coil wire and turn the key on... 

Edited by TiredBirds
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6 minutes ago, TiredBirds said:

the internal combustion engine needs 3 things...air, fuel and ignition. Since you smell gas I'd check for spark. Have a teammate hold the coil wire and turn the key on... 

 

I will have them put their tongue on the secondary side of the coil, similar to how you test 9v batteries.

8 minutes ago, NigelStu said:

How is the health of the battery?   IIRC, I had issues with my MS3 on my Miata when battery voltage was too low.

 

 

Check that and re-charge if needed.

 

Then follow Rob's check-list.

 

 

Also, does the MS completely take out the entire stock EFI and ignition system?  I had issues with that one special dual relay thing on my EFI Datsun, swapping to a good one fixed a start issue (but I don't know if that part is still on your car)

 

Will check the battery. 

 

all Datsun electronics is now gone, not a single datsun wire in the car.

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5 minutes ago, turbogrill said:

 

I will have them put their tongue on the secondary side of the coil, similar to how you test 9v batteries.

 

Will check the battery. 

 

all Datsun electronics is now gone, not a single datsun wire in the car.

also you need at least 9v at the coil. might turn over but not enough to light the fire. You'll get it.. 

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10 PSi is not enough to fire the injectors.  But, i would check for battery voltage, and spark.  Like others have said, Spark, Compression, fuel, and timing are the basic things to check for.

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Where are you testing fuel pressure.  You should have 40-45 psi cranking, especially with a wild cam.

 

The fat cam may also require more cranking RPM to fire than a normal cam due to the lower dynamic compression from valve overlap.  Make sure the battery is tip top.

 

Either you have an regulator, pump, or pump wiring issue.

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Whatever I did I couldn't get the regulator to regulate to more than 20 psi, this was with fuel pump only running and full voltage to the pump.

 

So something seems wrong with fuel delivery. 

 

Will investigate and let you know

 

thanks

Edited by turbogrill

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What happens if you manually pinch off the return line? If it doesn't increase pressure, I'd be looking at the pump or voltage to the pump.

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To repeat, check battery/system voltage when cranking.  I realize not Nissan electronics, but I have seen other (O.E. anyway) PCM/ECM that will not "compute" below ~10.5 volts.

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3 hours ago, wvumtnbkr said:

What happens if you manually pinch off the return line? If it doesn't increase pressure, I'd be looking at the pump or voltage to the pump.

 

Its steel braided so will be hard. I suspect something pump as well...maybe a cockroach built a nest inside the fuel pump.

 

1 hour ago, craig71188 said:

To repeat, check battery/system voltage when cranking.  I realize not Nissan electronics, but I have seen other (O.E. anyway) PCM/ECM that will not "compute" below ~10.5 volts.

 

ok! I currently get 8v during cranking. I think the Megasquirt are pretty robust against low voltage.

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7 minutes ago, turbogrill said:

 

Its steel braided so will be hard. I suspect something pump as well...maybe a cockroach built a nest inside the fuel pump.

 

 

ok! I currently get 8v during cranking. I think the Megasquirt are pretty robust against low voltage.

I don't think 8v is enough. Did you try "hot start" that should fire, if it does you know where the issue is. 

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3 minutes ago, turbogrill said:

Megasquirt are pretty robust against low voltage

That is not a correct statement as the ones I have built and run will do nothing in that voltage range. I have found you need at least 10.5 or more to make them work.

At lower voltage the can maybe fire once and a while but thats about it.

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2 minutes ago, 55mini said:

That is not a correct statement as the ones I have built and run will do nothing in that voltage range. I have found you need at least 10.5 or more to make them work.

At lower voltage the can maybe fire once and a while but thats about it.

I agree with the above. If you have your laptop connected to MS through tunerstudio you'll see a bunch of warnings pop up all related to low battery voltage. I normally just use jumper cables from another running car to up the cranking voltage. You should hear your coil relay audibly clicking on if MS is syncing with the crank. Pull a spark plug out will still connected to a plug wire and ground it on the block. Watch for spark while cranking. Even if you are having fuel delivery issues, some fuel vapor or starting fluid will be enough to hear combustion events if you have spark. 

 

Another thing to do since you have MS is to look at the cranking log in tunerstudio to make sure you don't have sync loss. I've fought that on a couple MS cars. 

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13 minutes ago, IPF Racing said:

I agree with the above. If you have your laptop connected to MS through tunerstudio you'll see a bunch of warnings pop up all related to low battery voltage. I normally just use jumper cables from another running car to up the cranking voltage. You should hear your coil relay audibly clicking on if MS is syncing with the crank. Pull a spark plug out will still connected to a plug wire and ground it on the block. Watch for spark while cranking. Even if you are having fuel delivery issues, some fuel vapor or starting fluid will be enough to hear combustion events if you have spark. 

 

Another thing to do since you have MS is to look at the cranking log in tunerstudio to make sure you don't have sync loss. I've fought that on a couple MS cars. 

 

+1 for hooking jumper cables to a running car.  

 

I just got my rx7 running on MS after maybe 4 months of banging my head against a wall trying to figure out why it wouldn't run. I finally found this weekend that when I clipped one of the injectors in, I bent one of the little tabs down so it wasn't connected.  Bent the tab back up and the car runs like a dream now.

 

If I can offer one suggestion it's Be Methodical. I spent months replacing every single piece of every system... and it was just a bent injector plug tab.  

 

Good luck!

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How are you measuring 8 volts during cranking?  If you're measuring at the pump with it connected, then the pump ground is suspect.  You should have nearly no voltage as the pump should be consuming most of it.  Only way you see voltage is if there is high resistance either in the wiring at the pump, the pump itself, or the ground circuit.

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37 minutes ago, SonsOfIrony said:

How are you measuring 8 volts during cranking?  If you're measuring at the pump with it connected, then the pump ground is suspect.  You should have nearly no voltage as the pump should be consuming most of it.  Only way you see voltage is if there is high resistance either in the wiring at the pump, the pump itself, or the ground circuit.

 

it's what the Megasquirt says in the log.

 

will try jumper cables

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7 minutes ago, turbogrill said:

 

it's what the Megasquirt says in the log.

 

will try jumper cables

 

I'd hotwire the pump first or pinch off the return.  You need to figure out why you're not getting fuel pressure.

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We run our fuel pump on a toggle switch on the dash  so we can see pressure all the time and easier for testing everything. If you run it off the MS it will only run to fill system 

and then stop until it see crank cycle and with low voltage may not be coming on during crank.

As said about run a hot wire to the pump and get it to full pressure with your return line to tank or cell there is no harm in it running at full pressure all the time when power is applied.

 

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30 minutes ago, 55mini said:

We run our fuel pump on a toggle switch on the dash  so we can see pressure all the time and easier for testing everything. If you run it off the MS it will only run to fill system 

and then stop until it see crank cycle and with low voltage may not be coming on during crank.

As said about run a hot wire to the pump and get it to full pressure with your return line to tank or cell there is no harm in it running at full pressure all the time when power is applied.

 

@55mini I think you're signature line needs to have "...and electronic guru" added to "the wrench."

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2 hours ago, 55mini said:

We run our fuel pump on a toggle switch on the dash  so we can see pressure all the time and easier for testing everything. If you run it off the MS it will only run to fill system 

and then stop until it see crank cycle and with low voltage may not be coming on during crank.

As said about run a hot wire to the pump and get it to full pressure with your return line to tank or cell there is no harm in it running at full pressure all the time when power is applied.

 

 

My only concern would be that the fuel pump would be running and squirting fuel on me while I am unconscious after crashing into a crown vic. 

 

But will try it!

 

thanks

Edited by turbogrill

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