Brand new engine...won't start

smith181992

Registered User
Ok guys, I've got a tricky one for ya! I finished my rebuild on my 90 supercoupe and I cannot get this thing to start for anything!

Mods while the engine was out:

.30 over Wiseco pistons with 94 rods
Custom grind cam from DD
75mm tb
42' injectors
73mm maf calibrated for 42' injectors
lots of port work

Things I have checked:

Triple checked the cam sensor timing and it is dead on
It's firing
the injectors are spraying
compression is good
fuel pressure is good
checked all my harness connections and vac lines a million times

The only thing that I think could be the problem would be my dis, considering I turned it over a few times without any heat sink underneath it (this was when the cam sensor was out of time, so it never started). The car isn't even trying to start, no backfire, sputtering or anything, just turns over. I'm currently out of ideas :confused: and really don't want to just go waste $70 on a new dis if that isn't even my problem. How can I check the dis?
 
I just went to check because I never checked all of them, and yes, all of them are firing, also rechecked my firing order and it is correct
 
Bet its the crank sensor if all the plugs are firing i doubt its the DIS

If the crank sensor is bad then nothing fires. At all. Clearly it's not the crank sensor.

If you tried to start it with the cam sensor not properly timed then most likely the plugs are fouled. Check a plug or two and see if they are wet/fouled.

If the plugs are not fouled then generally if it's not firing you probably don't have fuel. You said you have fuel pressure, but how do you know the injectors are firing?

If the engine has fuel and spark but doesn't start you did something wrong. Don't go replacing parts at random. Did you properly clean the connector for the chip? Both sides of the circuit board?
 
The '90 mounts the DIS on the accessory bracket, where there is a ground path that directly supports operations thereof.

Did you paint that bracket?
 
If the crank sensor is bad then nothing fires. At all. Clearly it's not the crank sensor.

If you tried to start it with the cam sensor not properly timed then most likely the plugs are fouled. Check a plug or two and see if they are wet/fouled.

If the plugs are not fouled then generally if it's not firing you probably don't have fuel. You said you have fuel pressure, but how do you know the injectors are firing?

If the engine has fuel and spark but doesn't start you did something wrong. Don't go replacing parts at random. Did you properly clean the connector for the chip? Both sides of the circuit board?

pulled all the plugs, cleaned them (they weren't fouled, but since I had them out, i did it). I used noid lights to make sure the injectors were breaking, they are, and when i pulled the plugs, they all had gas on them, so I know they are actually spraying. BUT, I haven't gotten in the chip yet, so the computer still has the stock tune on it, but I was told that with a maf calibrated for the injectors I'm running, it should run without a tune, is this correct?
 
The '90 mounts the DIS on the accessory bracket, where there is a ground path that directly supports operations thereof.

Did you paint that bracket?

I did paint that bracket, but i Taped off the section where the DIS mounts, I'm removing it now and I'm going to clean and put new heat sink again on it just for the heck of it
 
What size injector and how do you know you are using the correct sampling tube in your MAF? That could certainly be the issue.
 
What size injector and how do you know you are using the correct sampling tube in your MAF? That could certainly be the issue.

42' Injectors and a 73mm c&l maf with a green sampling tube for 42s. Took the DIS off again and sanded the surface, cleaned it, put new heat sink on, and even added a temporary ground cable to one of the dis bolts straight to the neg battery terminal just to rule out that problem. Still nothing
 

Well doesn't that just suck. So I wonder what I should do now?? David Dalke just sent me a chip out tuned for a green sample tube, So maybe when I get the chip, it will run? I don't see how it wouldn't sputter or anything considering the injectors are spraying, and since they are spraying, wouldn't that mean it was the correct sample tube?
 
The green sample tube will work without a tune, confirmed through DD as the guy I bought the maf from just showed me
 
I did paint that bracket, but i Taped off the section where the DIS mounts, I'm removing it now and I'm going to clean and put new heat sink again on it just for the heck of it

Bonus points for making it clean where it mates with the block, or that taped off mount area won't matter all that much :)
 
I did not confirm that green is the right color. I only asked Ben to make sure what calibration he had. I actually relied on his statement as I do not memorize all the calibrations. So that is kind of my fault. I just looked now and I see that red is the proper color for 42's in a 73mm.

I can re-write the chip for the green tube, but you'd have to send it back. The other option is to get a red tube but that's money down the drain. My apologies.

As for the no start, if the DIS is grounded and spark is happening, then it will start. Yes, the brackets have to be grounded to the motor just as the motor has to be grounded to the frame. Bolt threads are NOT sufficient for a ground connection. Always sand clean all contact points for bolts that might carry electricity!

But on to the more likely problem here. Trying to start the engine without a chip is just all bad. Yes, I know people will tell you that it will work, but why screw around? Injector pulse width (or start up fuel command) is based mostly on a fixed value meaning that during cranking there is nothing other than the chip to tell the injectors how much fuel to put in. Without a chip to tell it there are 42's in there you are going to get 40% extra fuel during crank. This will flood an engine very quickly if it does not start right away. Attempting to start it with the cam sensor set wrong AND 42lb injectors will render your spark plugs useless.

Then, to complicate matters further, as soon as the engine gets above about 150rpm (still cranking, not quite started yet), the EEC looks to the MAF for more accurate fuel commands. With a 50lb sample tube but 42lb injectors it won't get enough fuel to run. So oddly enough, you have a situation of flooding at initial crank followed by not enough fuel as soon as the first command kicks out.

After fixing the wet plugs condition it may fire up, or at least try to start, but chances are it may not run or at least not very well at all. And since the chip was written for a 42lb calibration meter rather than a 50lb cal, well the chip will only help just so much.

Sounds complicated I know, but if this is the biggest issue you have, consider it smooth sailing!
 
I did not confirm that green is the right color. I only asked Ben to make sure what calibration he had. I actually relied on his statement as I do not memorize all the calibrations. So that is kind of my fault. I just looked now and I see that red is the proper color for 42's in a 73mm.

I can re-write the chip for the green tube, but you'd have to send it back. The other option is to get a red tube but that's money down the drain. My apologies.

As for the no start, if the DIS is grounded and spark is happening, then it will start. Yes, the brackets have to be grounded to the motor just as the motor has to be grounded to the frame. Bolt threads are NOT sufficient for a ground connection. Always sand clean all contact points for bolts that might carry electricity!

But on to the more likely problem here. Trying to start the engine without a chip is just all bad. Yes, I know people will tell you that it will work, but why screw around? Injector pulse width (or start up fuel command) is based mostly on a fixed value meaning that during cranking there is nothing other than the chip to tell the injectors how much fuel to put in. Without a chip to tell it there are 42's in there you are going to get 40% extra fuel during crank. This will flood an engine very quickly if it does not start right away. Attempting to start it with the cam sensor set wrong AND 42lb injectors will render your spark plugs useless.

Then, to complicate matters further, as soon as the engine gets above about 150rpm (still cranking, not quite started yet), the EEC looks to the MAF for more accurate fuel commands. With a 50lb sample tube but 42lb injectors it won't get enough fuel to run. So oddly enough, you have a situation of flooding at initial crank followed by not enough fuel as soon as the first command kicks out.

After fixing the wet plugs condition it may fire up, or at least try to start, but chances are it may not run or at least not very well at all. And since the chip was written for a 42lb calibration meter rather than a 50lb cal, well the chip will only help just so much.

Sounds complicated I know, but if this is the biggest issue you have, consider it smooth sailing!

Thanks for the info David, I emailed you :)
 
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