RussellRat

So here are the details. Any help would be greatly appreciated. I've spent days trying to troubleshoot this and am getting a little wacky.

- I installed a new engine with MPFI. The computer is off of an early 90's Camaro. Everything is new, including all sensors, the harness, injectors, fuel pump, and electronics.

- The engine will not start. It shudders occasionally when cranking over like it wants to start. I got it to run pretty rough once, but the greyish smoke out of the exhaust made me think it was running rich. No catalytic converter to worry about either.

- The fuel pressure is good, steady at 43 psi. It holds pressure after the pump turns off and no fuel leaks out of the injectors. The injector spray pattern is good on all injectors, though it seems it puts out a lot of fuel just for cranking the engine over. The injectors pulsate and are not on constantly. They are 26 lbs and hour, which it is programed for. The spark plugs are all wet when checked after cranking. Even when wet, they spark nice and hot. All plugs have good spark. Timing has been verified many times. Distributor is pointing to number one when number one is at TDC. Wires are in the correct order and follow the correct rotation. If the timing is set too far back, the cylinders seam to fire easier, but they just push against they piston before it reaches TDC. Compression on all cylinders is good, all cylinders within 5 of 140 without oiling beforehand.

- I've tested just about everything. The TPS is at .5V closed and 4.5 open. The MAP has the correct voltage for key on and and goes down a little when cranking. The ECU is not in limp mode. The SES light comes on with key, blinks, and stays solid. No codes to speak of. I got a low TPS voltage code once, but it cleared when adjusted. The IAC is recieving voltage and is not stuck. One thing I did notice is the IAC position is always on 160 and the IDLE REQ is always at 3100, not sure if that is normal when cranking and it will only go down after starting. The CTS is reading the correct temperature. The spark plugs have been cleaned and have never had an issue sparking even when wet.

At this point I feel like it is getting too much fuel while cranking and putting the flame out, which explains a few things, but I can't figure out why! The injectors are on the smaller side for the engine.

Any help would be appreciated!

amlv20

cam timing or fuel quality good?

ninetyone

iTrader: (2)

First of all ,what car is the engine in? Brand new engine or used?

RussellRat

Quick responses! Thanks.

Fuel quality is fine. Only a couple weeks old. The fuel tank is new too so there shouldn't be any contaminants. Cam timing is fine. Timing chain was installed dot to dot and is new. I also think that compression would suffer if it was off by a tooth or so, not 100% sure though. I double checked valve lash. The cam is pretty mild too. Duration is barely above stock.

It's in an 80's chevy truck. Not much is original under the hood though. Most everything is early 90's TPI stuff. The lower half has about 5000 miles on it with flat top pistons. Everything else is new, including heads, intake, throttle body, lifters. The computer is from a 90-92 camaro or corvette.

Tuned Performance

iTrader: (92)

did you bypass the vats ?

RussellRat

Yeah, vats disabled.

305sbc

iTrader: (3)

Have you tried a fresh set of sparkplugs?
Have you tried putting the plug wires on the cap 180* out, just to be sure?

You can try reducing your cranking fuel by either warming up the CTS, or tricking it with a resistor or a POT. That is if you're convinced that it is too much cranking fuel causing the problem.
You could also visually check the IAC opening and then unhook it to eliminate it as a cause.

Have you tried plugging off all of your vacuum lines for testing/troubleshooting, to include the line to the brake booster?

RussellRat

I haven't tried a fresh set of plugs, but these things fire so bright I don't see how they could be the problem. It's consistent too. I haven't seen them stutter at all. Something about intake backfires sorta get under my skin. It's like the engine saying don't F$#& with me man! I might have to try both of those though just to make sure.

During cranking there was a good amount of air going through the idle port, so it's not plugged. Will the engine start with the IAC removed?

I tried blocking all lines and didn't notice a difference. I'll warm up that CTS tomorrow. It has been in the 30's here in Seattle so.... great Idea! There was even a little bit of liquid fuel when I removed the plugs today too, so pretty sure there is too much fuel.

myzblubyu

" The cam is pretty mild too. Duration is barely above stock."


Try 22lb injectors, 26lb is too big for a barely above stock engine.

RussellRat

The engine is stroked and bored 30 over, so the injectors should be fine. Even if not, they certainly shouldn't be so big that they stop it from running Even though they are new, I also ohmed them out at 14. I put in a fresh ECU and swapped the prom, but nothing changed.

I tried warming up the CTS to no avail, but thinking along the same lines, somebody else recommended restricting the fuel supply line with a clamp. I had to clamp it almost all the way, but it starts almost every time I crank it. It sounds pretty rough at idle, but too much fuel seems to be at least one of the major problems.

From what I've read, the MAP could be faulty, or the distributor could be sending the wrong RPM signal to the computer. Anybody have any experience troubleshooting either of those? I think the correct cranking voltage of the MAP would verify its operation. As far as the distributor RPM signal to the computer, I have no idea.

305sbc

iTrader: (3)

I often see that the factory calibration for cranking fuel is between 15% and 20% more than what is needed on a stock engine.
Your injector's max flow rating is about 18% more than stock injectors, - don't know how they compare at low pulse-widths. The difference may be greater.

You could try lowering your fuel pressure by about 10 psi and heating your CTS up to around 180* - 200*F as mentioned to lower the cranking fuel to see if that will get it running for a while.
If you can get it running long enough, try setting your initial spark advance up to around 15* BTDC (temporarily) and it may help with the rich starting until you can get the cranking issue solved or the chip retuned around it.

Most TPI calibrations will initiate "clear-flood" mode (less cranking fuel) for cranking by holding the throttle to 75% or higher before you crank the engine. I don't know if it will help in your case, but it's something to try.

305sbc

iTrader: (3)

wait, you have a 383 ?

A tight 383 will create a stronger cranking signal, and doesn't necessarily need more cranking fuel than a stock 350. A looser engine with a large cam might need more cranking fuel.
A tight 383 should create more cylinder pressure at cranking speed with a small duration cam, - unless the cam timing is out.

RussellRat

Do you think that 26lb injectors would flood a 383 almost instantly? Unless the injectors are spraying too much for some reason, I can't imagine they would be the problem. I also didn't remove all the spark plugs during the compression check. It was one by one so the numbers are lower.

The other day I sprayed some carb cleaner through the throttle body to see if it would start, after disabling the fuel pump. I didn't compensate for the residual fuel pressure in the rails and I think that might have killed the attempt. Today I cleaned the plugs thorougly, cranked the engine over for a little bit to get rid of any fuel pressure in the rails and fuel in the cylinders, and used actual starting fluid. It started up perfectly and sounded awesome!

I think there might be a problem with the program. The shop who wrote it swears there is not a problem, but I've tried everything except replacing the brand new injectors. The ignition module hasn't been replaced either. They are telling me that the module might be sending the wrong rpm signal to the ECU. Are they blowing smoke or can that actually happen?

Anybody know a good shop in the Seattle area? I have a few days before this thing needs to move.

Street Lethal

iTrader: (16)

Where is your BLM at idle, and do your IAC counts decrease when in Closed Loop? Are you even able to reach Closed Loop, or does the engine want to stall right away...

RussellRat

The engine idles perfect for five seconds, then very rough and stalls after the starter fluid runs out. The fluid will last me 5 seconds and it will idle for 5 seconds after that. Feathering the pedal will keep it running longer but never idling steady. It stalls if I keep the pedal farther depressed in one spot too. Haven't made it to closed loop yet. BLM is constant at 128 through 30 seconds of running. O2 fluctuates between rich and lean, but AF ratio was 11-12 the entire time. IAC starts at 160 and goes down and fluctuates between 100 and 120. When pressing the pedal the RPM acceleration is smooth. I'll try to reach closed loop tomorrow.

Street Lethal

iTrader: (16)

It's reading 43-psi with the regulator hooked up with 26lb injectors? That is too high....

RussellRat

So...my original injectors were bought as 26#'s, were packaged as 26#'s, but according to the little part number etched in there bodies, they are 39#'s. There goes a week of my life! Installing new ones now. We'll see how they work.

Street Lethal

iTrader: (16)

That sounds correct, especially since you said earlier in this thread that you pulled the plugs and raw fuel came trickling out. The ECM obviously cannot correct for that large of a percentage increase, and usually there is a 6% threshold with O2 correction, so 26 pounders would have been fine at the right fuel pressure. With the right injectors installed this time, be sure to set your fuel pressure with the regulator unhooked at around 43-45 psi, then when re-hooked it will read lower at idle...

SDTransAM

iTrader: (5)

Any updates? I'm kinda curious!

ozzy74

id say he's gone for a rip after all that bull s**t...lol

RussellRat

The engine still doesn't run well, or different from what it did. It still start great with starter fluid, and still runs shitty after the fluid runs out. I'm thinking about sticking a potentiometer on the MAP sensor to trick the computer into spitting out less fuel.

Had a mechanic stop by this morning who had no idea what was going on. He said the spark plugs might have to small of a gap. I'll double check to make sure.

You know when you were younger, and you had all those overcooked green beans on your plate? You thought, if you just waited long enough those green beans would disappear and your problem would be solved. That is sort of the mental state I am in right now. No speed shops in Seattle will tune this computer either. Nobody knows how.

Street Lethal

iTrader: (16)

What exactly did you do that was different, did you put in the correct sized injectors yet? You also didn't answer my question. Is the fuel pressure reading 43-psi with the regulator hooked up, or disconnected? The fuel pressure should be set to 43-psi with the regulator unhooked (wot setting), then when hooked back up, the pressure should read lower than that at idle. If it's reading 43-psi at idle with the regulator hooked up, then the regulator is pressurizing the fuel for wide open throttle, which is too much at idle, add to that much larger injectors than what the prom was burned for, and your excessively running rich. You need to once again explain your setup. What size injectors are you running now, 26 pound or 39 pound, and how are you setting your base fuel pressure...?

RussellRat

Yeah, sorry I did't respond directly to that. I verified the fuel pressure and it holds at 43 psi after the engine is off and drops into the mid thirties when running. It is never steady when running because engine vacuum is so random since a steady RPM can't be maintained. When I said it holds steady at 43, I meant steady after I turn it off just to be clear there were no injector leaks. It has verified 26lb an hour injectors in there now. I had it running for a couple of minutes, but couldn't get it into closed loop, and the spark plugs were pretty fouled. It also had an est fault, code 42, when est was connected, so I have to go figure out why that might have happened. It was the first time though.

Street Lethal

iTrader: (16)

Code 42 will be tripped if you pull the EST bypass with the battery connected when setting your timing, quick fix is to disconnect the battery then reconnect it again. You said you are positive that your timing is correct, and that your plug wires are routed correctly, so we'll just move on from there. If the fuel pressure gauge is sporadic because of a rough idle, the first thing you will want to confirm is the absence of any vacuum leaks. If there are no leaks prevalent, then target your rocker arm adjustment because if they are skewed (some too tight, and some correct), then the engine will run very rough, and even stall, because the valves will not close in some cylinders. To reiterate, check for vacuum leaks, and readjust your rocker arms (valve lash), then we'll move on from there...

ninetyone

iTrader: (2)

Your fuel pressure should be measured with engine running and the vacuum hose plugged. Should be at 43.5 psi.

RussellRat

That's where it's at. Though I get why street lethal says measure while running on top of that, to make sure the engine vacuum is acting on the FPR diaphragm.

Something I just noticed when goofing around... only with my tach disconnected do I get good spark. Once it is connected, the spark is too weak to even start the engine. Maybe I have a bad ground somewhere.

RussellRat

There are not very many vacuum connections, and have checked everything short of removing the manifold completely. Vacuum is good for the few seconds the engine is running smooth. Over 20. It only drops as the engine starts to stumble. At higher RPM's, say 2500-3000, the engine still stumbles and dies if you keep the pedal in the same place. I agree it does sound like a valve lash or cam timing issue. The only thing that throws me off is that during the few seconds on starter fluid, it runs baby smooth. I checked preload on all the rockers earlier, and everything was perfect, unless made some simple mistake. If that was a problem though, I don't think it would run smooth at any time. I'm running out of things to check though, so I guess it wouldn't hurt to do it one more time!

Street Lethal

iTrader: (16)

Does the engine at least run smooth all the way to Closed Loop with the tach disconnected?

RussellRat

No. I haven't made it to closed loop yet. with the tach connected, it won't even rumble a little. There is spark at that point, it is just very weak. When the tach is disconnected, the spark is nice and blue. Had it running for 2-3 minutes max and it never went into closed loop. Feathered the pedal the entire time. It got harder and harder to keep it going. If the throttle stays in one place too long, it dies. After the two minutes, the plugs start looking pretty black. It's either an incomplete burn, or too rich of a mixture. Since it runs really well on starter fluid, I'm thinking too rich and the flame is being put out. I have no idea why the computer would call for so much fuel though. Fiddled around with lower pressure and dropped MAP voltage to no avail.

Street Lethal

iTrader: (16)

Do you still have the stock prom that came with the ECM available to you...?

RussellRat

Great idea, but no, don't have an original. I might go hit up a junkyard for one.

305sbc

iTrader: (3)

Just a stab in the dark here. By chance have you had someone watch your damper with a timing light while you start the engine with the starting fluid to make sure the ECM is advancing the timing up off of your base setting when the engine starts and revs?
I'm not suggesting you have a timing problem, but the ECM does use DRP - distributor pulses in order to determine injector firing cycles.
If the ECM isn't advancing the spark properly, that might point you in the right direction.

rgarcia63

In your 1st post you said it would not start and the fuel pressure was steady at 43.5psi, this would be your highest pressure so when the engine starts vacuum is high lowering your idle pressure to around 35psi because not much fuel is needed at idle.

If the quality of the spark is better with the tach disconnected, leave it disconnected, you can read the rpm with a tuner program, or a data logger and fix that problem later.

305sbc

iTrader: (3)

http://www.chevythunder.com/est_code_42.htm

ninetyone

iTrader: (2)

I wonder if you have the 2 connections at the coil reversed. Or the two at the distributor module. Just a thought. Heard it happen before.

DBRjeep350TPI

I have a similar issue i am fighting right now... almost exactly. Are you running good spark plugs? Plugs in the right heat range? Also have you checked the resistances across your plug wires to make sure all of them are okay?

RussellRat

I gave up! Well sort of. I went with an aftermarket computer that was compatible with all my sensors and fuel system. It didn't warm up perfectly the first time starting, but idled smooth after a minute of running and starts up every time now. It's even in the 20's tonight in Seattle!

You might have been on to something. It did turn out to be a computer related issue. The injectors were definitely putting too much fuel out, and among other things, the ignition signal to the computer could have been at fault.

Yeah, I only noticed it twice, because most of the time it was disconnect. For 95% of troubleshoot, it wasn't a factor.

Great link! Thanks.

It was definitely on the right side. I think for some reason my tach is acting as a large load in series with the coil, so the voltage drop across the coil is less than it should be. Haven't spent time trying to figure that out yet.

My issue was definitely related to the injectors staying open for too long and putting out to much fuel. The aftermarket computer is like night and day. So, I will call it either a program issue, or an ignition signal issue. All sensors were good, fuel delivery was perfect, and there were no vacuum leaks. a Known good computer was installed during troubleshooting with no affect, so I don't think my computer was faulty. All the wiring was new, and every voltage and impedance check I did was good.

I was thinking that the plugs were protruding into the cylinder too much, but they work fine now and are not fouling anymore.

If you have a stock engine and program, I would make sure that the ignition wires are not close to or touching the harness. I heard that the electromagnetic field generated by the high voltages can interfere with the ignition signal. If it is a new install with a custom program, you have a couple extra areas to check. If I had time I would have bought the hardware require to look at my program, so if you are up to it, that's an option!

DBRjeep350TPI

you say you went with an aftermarket computer... you mean a new memcal chip? A custom burnt one? I am curious. I am running a Hypertec thermol chip and curious if that might be the root of my problems? where did you get yours? I know that might be an option to get the program and hardware to look at it myself, but I would like to have one just burnt to the application I have and call it done.
Also you mention that ignition wire touching or to close to the "harness", what harness are you refering too?
thanks

RussellRat

I actually went with a new aftermarket system. It was EZ EFI for multiport kits. It uses early GM sensors, so it was compatible with everything. There is one place that sells it for less than $800, and it uses a wideband O2 sensor. The only drawback is no knock protection and no timing control, so I had to use a carburetor based dizzy, though it starts with the old one just fine!

The things I learned that could feed the engine too much fuel are:

1. Low vaccum causing the MAP sensor to over compensate.
2. Bad MAP sending too high voltage. Should be 1 to 1.5 v at idle, and around 4.5 at WOT
3. CTS reading too low a temperature
4. Throttle position sensor. Should be at .5 to .6 at idle, and above 4 at WOT. But the computer compensates for this too.
5. Injectors too big.
6. Injectors staying open too long
7. Injectors stuck open or leaking
8. Too high of fuel pressure.
9. Ignition module RPM output to computer is too high

Maybe there are others, like bad computer, but that should be most.


Mine ended up being number six, injectors staying open too long. That can only be caused be the computer telling it to stay open too long. This would either be a computer problem, a program problem, or a harness problem. I've read that errant electrical signals could distort certain signals going to the computer. The best way to check would be a to verify on a scanner, but certainly make sure your wiring around the dizzy is clean, no wiring touching the spark plug wires and such. That's all I meant by keeping the harness away from the ignition.

DBRjeep350TPI

thanks for the information!!! I am going to check the voltage and also the wires interferance.
then again 800 bucks is not a bad move, that cost is the extra fuel being dumped and a buying and changing sensors.