Trouble getting LS3 to come to life

[dreabrown]

Well this week was supposed to be a time to celebrate the first start of GTM #357. Unfortunately, my "slightly used" LS3 is showing NO signs of life.

When I turn on the ignition I hear the fuel pump running and fuel going to the fuel rails. When I crank the starter it turns over fine, but no signs of starting beyond that. In fact, I don't seem to be getting any injector pulse or ignition spark. I checked all connections to all sensors, all power connections, and grounds (~3-4 times!). Everything is hooked up fine. I even went so far as to change out the Cam sensor and Crank sensor thinking the ECU wasn't seeing the engine turning over causing starting difficulties. Drilling down further on the diagnostics I'm getting no trouble codes from the ECU but it also doesn't seem to be getting info from all sensors.

I'm using the ISIS system, and in talking to the supplier who sold me the engine, custom harness, and ECU there are some reports out there of people having similar trouble with ISIS in the mix. He also told me there is some sort of security mode that is tripped if the power connections to the ECU aren't right.

I realize this could be a million things, but does anyone have ideas about next steps to diagnose this problem? Is there a known issue with the ISIS powering the ECU adequately for starting conditions?

I'm ready to bring this build to life but I'm totally stumped. Thanks.

[VRaptor SpeedWorks, LLC]

I've used ISIS on several builds here with no issues at all. You don't have the ISIS "start" output tied directly to the starter solenoid, do you? It needs to be ran thru a relay. Are you guessing that there is no spark and no injection pulse, or have you physically checked them? If you haven't actually verified that you have no spark or injector pulse or fuel pressure......that is where I would start. I would start with spark and go from there.......if you have no spark, you know that the engine won't start no matter what else you do.......and also tells you that either you have something physically wired wrong, or, for whatever reason, the ECU is not seeing the engine crank.....or not sending out the outputs to provide spark. If you do have spark OR fuel injector pulse, then you know for a fact the ECU is seeing the engine crank. Do you have a heavy ground strap from the engine to the chassis and all of your engine harness grounds properly grounded?

[Kempo]

As long as the ISIS output for ignition power it's turning on there isn't any other problem it might be causing. Apparently it is turning on because your fuel pump its priming the system. The PCM sends the fuel pump relay the signal to turn on the pump. You might be having problems with the VATS (vehicle anti theft system) that its embedded to most GM PCMs. The PCM must be looking for other sensors in the original donor that are not present in the GTM. And that would give you a no start condition althoug the engine will turn over just fine. The VATS can be disabled in the PCM using HPtuners, EFI live or similar tuning softwares. Make sure that it is indeed disabled. Hope this helps and congrats on reaching the first start stage.
H

[dreabrown]

Shane,

I have physically confirmed no injector pulse AND no spark with appropriate diagnostics. This is why I assumed the ECU wasn't sensing that the engine was cranking and changed the crank and cam sensors. That didn't fix the problem. The engine is fully grounded to the chassis and the harness I'd grounded to the block. Unless there is a wire crossed or cut in the harness ( which I didn't build) all connections are correct.

You mentioned running the start circuit thru a relay, does the ignition output from the ISIS to the harness (which obviously powers the ECU) also need to be run thru a relay? Could the injectors/coils be getting to little current directly from ISIS?

Thanks for the input. I'm going to get a few relays later today.

[dreabrown]

Hugo,

I was told the ECM was flashed for this configuration of sensors but you raise a good question. It's acting like its in security mode. I got several more questions for the supplier. I'll find out.

Thanks, EB

[crash]

Shane,

I have physically confirmed no injector pulse AND no spark with appropriate diagnostics. This is why I assumed the ECU wasn't sensing that the engine was cranking and changed the crank and cam sensors. That didn't fix the problem. The engine is fully grounded to the chassis and the harness I'd grounded to the block. Unless there is a wire crossed or cut in the harness ( which I didn't build) all connections are correct.

You mentioned running the start circuit thru a relay, does the ignition output from the ISIS to the harness (which obviously powers the ECU) also need to be run thru a relay? Could the injectors/coils be getting to little current directly from ISIS?

Thanks for the input. I'm going to get a few relays later today.

Just for reference, I recently did a wiring harness for an LS3 and at first used 15 amp fuses for the coils and injectors. That would be 4 seperate fuses. One 15 amp for the drivers side coils, one 15 amp for the drivers side injectors, one 15 amp for the passanger side coils, and one 15 amp for the passanger side injectors. I am also running heated wide band O2s and they were coming off the same circuit as the coils. I blew the 15 ampers on the coil circuits and had to increase them to 20 amp fuses. That's a total of 70 amps of available power there, so YES you do need to make sure you have ample supply to the coils and injectors.

Also, if the circuit to the computer isn't constantly above 12 volts, it may present a problem. This can be due to wiring sizes, wiring configuration, or battery condition under cranking mode. Check the voltage AT THE ECU when cranking. My particular computer was fine down to about 10.5 volts under cranking, but the point is that there IS a break point where the ECU will not function properly. I'd say if you are seeing 11-12 volts at the ECU you should be fine. If it is more like <10 volts, then you may have an issue.

[VRaptor SpeedWorks, LLC]

If your engine harness is like most aftermarket engine harnesses, it should have it's own fuseblock attached that has fuses and some relays installed, right? Normally there should be a heavy wire/cable that runs from this fuse block to the battery/main starter cable and THIS is where the engine harness gets its power from......all the ISIS "IGN" wire does is trigger a relay that powers up the whole fuse block.....OFF OF THAT HEAVY CABLE that comes from the battery/starter.....so generally, the only thing that ISIS wire is powering is a relay coil that pulls less than a quarter of an amp. I don't know if this is the way your engine harness is configured or not, but all aftermarket/GMPP crate harnesses I've dealt with so far are like this. Generally there are a ton of pink wires in the harness that should get 12v once the ign is on. I would confirm that you are at least getting power to all of those wires/fuses in crank mode and ign on.

[LCD Gauges]

It does seem like a security issue based on the symptoms, but if your PCM has VATS disabled, you should also prove the connections back to the computer.

Ensure that the crank pulse is getting to the computer.

Also check the voltage at the sensor, as well as the ground lead.

The Crank Position Sensor is what the computer needs to fire the coil(s), and injector pulse as this indicates the piston position through the cycle.

EDIT: Scratch that, you're getting no codes.

On a side note: How intrusive is the ISIS with respect to engine start? What other functions besides starter solenoid, and fuel pump power will it interrupt?
Does the ISIS also output voltage to the ignition wire for coil/injector power?

[dreabrown]

IMG_0911.jpgAttachment 13084OK, I've made some good progress figuring out the issue(s). I ran power thru a new fuse block with each of the 4 power wires feeding my harness run on on individual fused circuits. I now have spark and fuel injector pulse. I must have had insufficient power going to the ECM. I rechecked the ECM once this condition was fixed and still NO trouble codes. I then checked fuel pressure at the rails - NO pressure at all despite the fact that I hear the pump cycling when I turn on the ignition. I pulled the fuel pump thinking it was either blocked or defective (less likely since it is brand new). When I pulled it out of the tank the problem became obvious. There is open connection on the bottom of the pump assembly that was part of the original duel tank assembly that probably needs to be capped to generate fuel pressure!!! I don't remember seeing this step in the FF fuel tank prep directions. Is this true? If so, what have others used to cap this that will withstand the high pressures and not degrade in fuel?

Thanks for all the good advice. Almost there....

EB

[VRaptor SpeedWorks, LLC]

Short chunk of rubber fuel injection hose plugged with a brass hose barb fitting with a brass threaded cap.

[dreabrown]

Anything with a clamp has the potential for failure. I wonder if something like this might provide a more secure solution. http://www.russellperformance.com/mc...fuel-efi.shtml.
No sealant needed I assume?

EB

[VRaptor SpeedWorks, LLC]

I've never had a proper fitting hose.....installed onto a hose barb with a proper fitting clamp fail. Usually, when taking apart such connections, I end up having to cut the hose off of the hose barb....once it has been on there and clamped for any amount of time, it's virtually impossible to get off, even after removing the clamp. No, I would not install the hose directly onto the smooth port off the bottom of the pump......use the quick-connect that was on there, and cut the hose off of the hose barbs of the quick-connect, install a new hose and plug and the proper clamps. Heck, the OEM fittings don't even HAVE clamps on them.....just the hose barb ends shoved into the plastic hose.

Yes, those fittings you linked to look like they'd be the hot ticket for this, but I don't see any prices listed for them. I don't imagine they are the cheapest things in the world?

[sressue]

Anything with a clamp has the potential for failure. I wonder if something like this might provide a more secure solution. http://www.russellperformance.com/mc...fuel-efi.shtml.
No sealant needed I assume?

EB

dreabrown,

I did use the Russell Push-on EFI quick disconnect male fitting with a AN cap and it seams to work just fine. I first tried rubber caps but the pump blew a hole in them twice so I went the extra cost and went with the Russell fittings. If you go with these fittings be sure to use a little lock tight on the cap.

[dreabrown]

LS3 Lives!!! I put on the Russell fitting, closed up the tank, and hooked up all the wiring again. The engine fired right up. Awesome moment!!! I'll post a vid when I download it from my phone. It idled a little rough, but I still don't have the MAF sensor hooked up. I just have the air filter element on attached directly to the intake.

Now I can focus on the short to-do list to get to the first drive. Check for leaks, rough alignment, and secure loose items and I'm ready to roll. This is the fun phase after a few months of frustrating moments.

Thanks for all the help. This community is awesome.

EB

[Edgeman]

Thats great new, I am waiting for my trans axle to get my LS3 running.

[LCD Gauges]

That's awesome! Good to see you figured it out in a short amount of time.

I'm a couple of weeks behind your lead; looking forward to your video.

[efnfast]

I sure as hell wouldn't trust Russel fittings - bottom of the barell for quality. Also, their GM fuel rail fittings used to just randomly pop off and set cars of fires (search for it, loooots of fires).

Only use Earls, Aeroquip or Aeromotive. Aeromotive makes several GM EFI clip on pieces.

[The Stig]

I sure as hell wouldn't trust Russel fittings - bottom of the barell for quality. Also, their GM fuel rail fittings used to just randomly pop off and set cars of fires (search for it, loooots of fires).

Only use Earls, Aeroquip or Aeromotive. Aeromotive makes several GM EFI clip on pieces.

I agree 100%. Go with Earls / Aeromotive. Much higher quality.

I am also having a bit of an issue starting my car after it has been sitting. When I hit the start button the first time, I can hear the pump run for about 4 seconds to presurize the fuel system. Then I hit the starter, and it just turns over and over. I go through this about 4 or 5 times and then it finally starts trying to catch and then starts up. If I run it for a few minutes and tuen it off. I can start it right back up with no problem. But if I haven't started it for a while, (like a weel or two), I have this issue. It's obviously getting fuel, or it wouldn't start at all.

But it seems that the fuel bleeds back down out of the lines, and it takes the sytem a bit to prime itself back up to allow the car to start. I'm thinking that a check valve may be in order. I thought that the pump itself would keep the fuel system pressurized. I guess I was wrong about that one.

Any thoughts?

[crash]

If you do a search on the other forum in regards to "fuel check valve" IIRC you will find the answer to your issue. Stock setup, I believe, always has an anti bleed back check valve.

[LCD Gauges]

But it seems that the fuel bleeds back down out of the lines, and it takes the sytem a bit to prime itself back up to allow the car to start. I'm thinking that a check valve may be in order. I thought that the pump itself would keep the fuel system pressurized. I guess I was wrong about that one.

Any thoughts?

it would seem that your check valve is faulty.

During start up the PCM commands a preset time to pressurize the fuel rails. if you wait too long, the rails bleed down, and there will be insufficient pressure and fuel volume to start the motor.

you may correct this by installing a check valve, or keeping constant power to the fuel pump during startup.

the latter is how my fuel system will be set up.

edit: may also be a faulty regulator

[LCD Gauges]

I sure as hell wouldn't trust Russel fittings - bottom of the barell for quality. Also, their GM fuel rail fittings used to just randomly pop off and set cars of fires (search for it, loooots of fires).

Only use Earls, Aeroquip or Aeromotive. Aeromotive makes several GM EFI clip on pieces.

At the risk of taking this thread off topic, here are my experiences with AN fittings:

Over the past ten years, I've been using a mix of all fittings listed except Aeroquip.

The only Russell product that failed was a 12AN, 90 degree swivel which dripped fuel after a few weeks of installation. The problem may have been
Too short of a braided hose which was turned too tightly of a radius to connect a fuel pump. Making a longer hose with less stress might have prevented
the problem initially, which is what was required. The fitting was replaced as well.

It may be an issue that Russell has a teflon hose which requires a unique
Fitting . I have seen, and read about people interchanging these systems which is guaranteed to cause leaks, and pop hoses because the ID/OD,
and the hose materials are different.

There is also a tendency for the fittings to creep up the hose as they are threaded
To the collar. this will also promote
failure of connection.

I've had one Aeromotive pump fail in a customer's car w which luckily was covered under
Warranty.

I have no preference of brand, and my car uses a mix of Earl, and Russell.
They are equally good in my opinion. My regulator is Aeromotive which I think is a quality
Piece.

[crash]

The only Russell product that failed was a 12AN, 90 degree swivel which dripped fuel after a few weeks of installation. The problem may have been
Too short of a braided hose which was turned too tightly of a radius to connect a fuel pump.

HOLY SCHIZA! You had something with a -12 FUEL LINE?!? Please, I gotta know what that project was. Did it use a toilet bowl for a carb?

[LCD Gauges]

My bad, it was this 90 degree fitting which is a -10 AN

Thought the A1000 was -12 AN Inlet/Outlet. In any case, this pump was STILL overkill for the setup. 11 second car, 500-600 HP.

compare_fuel.JPG

Just to compare the above with my Camaro: using stock fuel rails, fuel lines, and pump, the car put down 437 HP at the wheel, and
ran 12.51 @ 116 on street tires. It likely had room to grow yet.

Don't believe the hype.

[crash]

Yep. -8 is good to 1500+ HP. That's why I was asking, and probably still would have if you said -10. That's WAY overkill.

[LCD Gauges]

Hellz ya.

Now how do we tell the bench racers they don't need half inch fuel line for 500 HP?

[efnfast]

At the risk of taking this thread off topic, here are my experiences with AN fittings:

Over the past ten years, I've been using a mix of all fittings listed except Aeroquip.

The only Russell product that failed was a 12AN, 90 degree swivel which dripped fuel after a few weeks of installation. The problem may have been
Too short of a braided hose which was turned too tightly of a radius to connect a fuel pump. Making a longer hose with less stress might have prevented
the problem initially, which is what was required. The fitting was replaced as well.

It may be an issue that Russell has a teflon hose which requires a unique
Fitting . I have seen, and read about people interchanging these systems which is guaranteed to cause leaks, and pop hoses because the ID/OD,
and the hose materials are different.

There is also a tendency for the fittings to creep up the hose as they are threaded
To the collar. this will also promote
failure of connection.

I've had one Aeromotive pump fail in a customer's car w which luckily was covered under
Warranty.

I have no preference of brand, and my car uses a mix of Earl, and Russell.
They are equally good in my opinion. My regulator is Aeromotive which I think is a quality
Piece.

Just google all the failed Russel fittings and you'd steer clear of them. To their credit, when their clip-on EFI fuel rail fittings randomly popped off, pouring gas ont he headers and setting cars on fire, they did redesign them, but basically told customres to go f*k themselves if their car burnt to the ground because of their product.

Also, I love aeromotive fittings, good quality, but hate their piece of crap pumps - I had 3 SS external pumps, 0 miles on each one, and each one POURED fuel from the joint whenever I would start the car and temps were under 0*. Their answer - it was a 'safety feature for cold weather operation'. Bull**** - it's called dissimilar metals and the wrong o-ring.

[LCD Gauges]

I've tried searching Google with instances of Russell, AN fittings, fuel, and fire in the string.

Can you post a link? Id like to read on the EFI connectors because they are new to me, and they are currently installed on my car.