ascalise

iTrader: (2)

I just got my engine and trans in the car. Before i get started i want to mention that the factory 350 tpi ran perfect with no ses light or trouble codes. Well, i built a pretty wild 350 and used a converted LT1, 58mm bbk, and some 36lb accel injectors that were said to be as new. I had the prom burned by alvin at pcmforless. I deleted egr and smog. Well i got everything together and turned the key. Could not get it started for the life of me. I might as well mention now that i used the accell afpr and left it at the stock setting. I haven't changed the pump yet, its still sitting here on my bench. Anyway we got it started by dumping a coke cap full of gas in the plenum. It wouldnt idle and ran really crappy from around 1500rpm-3000rpm. I had to hold my foot on the gas quite a bit to keep it going. Once it was going, it wouldn't run out of fuel. It seemd to run fine above 4,000rpm but anything below was super rich and rough. When i'd turn it off you could see all of the raw gas vapor coming from the TB if you opened it. If i put my foot on the gas and turned the key it would start right back up but still not running properly. Anyway, since then it seems like i've been going backwards. I tried the factory (LT1) injectors that the manifold came with and it did the same thing only it would lean out and backfire out of the tb above 4k rpm. So, i decided to change the prom with the one that came with the car (hypertech). Same problem! Since then i've tried several things, checked timing again, cleaned plugs, and used vacuum pump to pump up map sensor to see if it would hold an idle. Same problem. Fuel pressure seemed fine as the rails would hold pressure and it would fire back up with foot on pedal. Now, i can't seem to get the rails to hold pressure. If i pull the supply line off before it would spray everywhere, now it doesnt. If i put a gauge on it it goes up to about 28psi while the pump is priming then immidiately goes back down when the pump shuts off if it isnt cranked. If i crank on it with the gauge attached it goes up to about 33-34psi. Seems to me like it should hold that pressure even when the pump stops priming.

Now, for the real trouble. I got a noid light to see if injectors are pulsing which i assumed they were since it would run after i dumped a little gas in to get it going initially. Well, i get no pulse. So, i check grounds and they all test good. I run the ignition module to autozone, it checks out good. So i grab a new pcm and it does the same thing. With the key off i would get 12v on both pink and dark green or dark blue injector wires while the testlight was grounded. When the key was turned on the dark wire would no longer have 12v with the key OFF?!?!?! I've read this is supposed to be normal. I assumed it wasnt which is why i bought a new pcm. So i disconnect all injectors and take the rails off and use my vacuum pump to see if rails or injector seals are leaking. It holds about 20" vacuum fine. I put the rails back on and break out the test light again while ALL injectors are unpluged. If i ground the test light and probe the two leads, the pink wire will show 12v with key off and the dark wire will show nothing. With the key on the dark wire will light the test light (still grounded) now. And stays lit while cranking. Now here is the part i cant figure out, if i move the clip on the test light to the positive post on the battery, the dark wire shows the exact same results. OFF with key off, lit with key on and while cranking. Just on hour before both leads would light the test light (12v). Either way the noid light does nothing when hooked to any injector harness while cranking. I am completely stumped. Someone please throw some ideas at me. All grounds check out ok, all fuses check out ok, and module checked out ok. What else is left?

RBob

iTrader: (1)

I can see where there may be a couple of areas that may not be quite correct. When using an aftermarket adjustable regulator it is normal for the fuel pressure to drop off once the pump shuts off.

The fuel pressure should be between 43.5 and 47.5 psi. That is factory stock. Hot wire the fuel pump on and set the fuel pressure within that range. If you can't set it within that range then it is probably time to put the new pump in. Or the FPR is bad.

Can also open the TB and listen for any injectors that are spraying, which would signify a leaky injector (done with FP running).

Noid light and injector wiring: unplug all of the injectors. With the ignition switch off the pink wires should not have power on them (there is a PNK, then a PNK/BLK, two separate power feeds). With the ignition switch on they should have power (noid light to ground). There are two fuses, INJ1 and INJ2 for these power feeds.

The DrkBlu and DrkGrn are grounded by the ECM in order to fire the injectors. They are also tied together inside of the ECM, so they should both be the same signal.

Placing the NOID light between the two pins of a single injector should have it flashing when cranked. Otherwise it should be off.

Can also use an ohm meter and check the resistance of each injector. It must be above 12 ohms. If lower then the winding is starting to short (common with Multecs). If higher then 16 ohms then the winding is going open).

Injectors, wild engine, and tune: the LT1 injectors are a little larger thent he stock 350 injectors, the 36#/hr injecotrs are a lot larger then the stock injectors. With the 36# injectors the engine won't run with the stock chip, too much fuel.

Then depending upon how radical a cam is in the engine, it won't run too well at low speeds. This is dependent upon the custom tune you have. Stock chip with the LT1's will probably be rich at low speeds and lean out at higher speeds.

Start at the begnning and set/check each item. IOW: get the fuel pressure squared away, then the injector power, then injector resistance, . . .

Then work on getting it running, data log, and get back to Alvin.

RBob.

ascalise

iTrader: (2)

I checked the resistance. They were all 14.2-14.4 ohms. My next step is to put the walbro pump in. I'm still a little confused as to why the injectors dont pulse. It seems to me that the wiring/signals are good at the injectors.

Z69

The ecm grounds one side of the injectors. The other side is keyed 12v. If the ecm doesn't have the one side grounded.
You will get 12v on both wires to the injectors if they are plugged in.
A bad conection on the gnd side would stop them from firing.
A failed VATS check will make them not fire too.
A bad ecm too.

ascalise

iTrader: (2)

i just bought a new ecm and wasted another $70 :-( the vats has always worked. worked fine with factory motor.

Z69

Not really, you can always use it to verify that the ecm is not the problem when trouble shooting. You just paid extra to buy one that for sure works. The JY route takes a little creativity if you get a bad one to get it replaced.

Does it at least sort of run still?
It's hard to keep track.

ascalise

iTrader: (2)

No, its really difficult to get started. When it does start i have to hold my foot on the gas quiet a bit and it will eventually foul the plugs.

Z69

It sounds like the chip is wrong. Maybe a bad MAP sensor.
You might try the 24lb injectors if they are good and the HT chip.
See if it starts any better. Not too hard on an LT1 at least.
You really should get an ALDL cable and TP.
Then you could scan/log and see what's going on.

ascalise

iTrader: (2)

i have tried the 24lb injectors and the ht chip. still wont start without foot on gas and runs rich at low rpms and leans out above 4k.

RBob

iTrader: (1)

How wild of a cam is in this engine?: "Well, i built a pretty wild 350 . . ."

To me it sounds like you need a lot of tuning done.

RBob.

ascalise

iTrader: (2)

comp cams xfi 12-368-4
248/253 @ 0.50"
.584/.579

87tpi7749

Just throwing this out there as a possibility, but is it possible that the fuel pressure reg has a torn or improperly assembled diaphram and raw fuel is going into the plenum via the vacuum hose. Take the vacuum hose off and check for fuel. I had this happen to me, symptoms were similar. It happened after I pinched off the return with a walbro 255 pump, it tore the diaphram & raw fuel was just pumping into the plenum. Had to almost use clear flood to start, reburned chips all day, finally found the extra fuel.

ascalise

iTrader: (2)

I already checked that too. Its a brand new accel afpr.

Lo-tec

Something is way off here. If it runs that fat with a 24lb injector, it shouldn't even run with a 36lb one in there. I'd call and verify what injector the chip was burned for. I started my engine with 36lb injectors in it, thought the tune was for 36lb injectors, but was for 24lb ones. Needless to say, it was very hard to start, ran like poo and was really really really rich. I don't know why it even started.

Do you have access to a WBO2?

What do you have the timing set at, and how did you set it? Have you tried moving the timing around, or looked to see what it was doing with the engine running?

RBob

iTrader: (1)

Yep, with that cam the engine will run exactly as you are seeing. Rich down low and lean up top. You need to get with your chip tuner and have him straightened it out. the spark timing will also require a bit of work.

RBob.

ascalise

iTrader: (2)

he says it should only require minor tuning. he mentioned that it should start right up and idle just fine. he says he does these with the 730 and speed density all of the time with cams like this.

RednGold86Z

iTrader: (1)

I'm guessing that you need to get the base timing adjusted a LOT better. Loosen the bolt that keeps the distributor in place, and have someone keep the engine running for you, and twist the distributor until it gets much better. Then get a timing light on there, and try to get the base timing to 12 or more, and get the chip burner to set the base timing in the chip to 12 or more for that cam (or find out if he already has).

Hope you're running a LOT of compression with that one.
Good Luck!

ascalise

iTrader: (2)

Timing is not the issue. We played with that until we were blue in the face. Its as close to it's best right where it is. Base timing cant be set without the car idling anyway with a timing light.

RBob

iTrader: (1)

As for the issue of needing to hold the throttle open a little with the go pedal, during crank and run, check that the IAC passage from the BBK TB lines up with the LT1 intake. It may not which will cause a lack of IAC air.

RBob.

ascalise

iTrader: (2)

That passage is no longer there but i have been told by 5 different people including the previous owner of the intake that it is not needed. He said he ran his car that way for 8 months before selling the intake to me.

87tpi7749

Did it run good? RBob is pointing you in a good direction. The iac valve and passage provide air for combustion during closed throttle, the valve & passages bypass the throttle plates, if you don't have the ports, then the iac is meaningless. The other guy probaly had the base idle cranked way up. Double check the iac passages, it may not be your fix, but it may need fixing.

Z69

Not true, the passages in the LT1 distribute the idle air and EGR to each individual runner for hopefully a more equal distribution to each cylinder.
It's common for people to just hog out the whole TB mount pad to look like a mini ram when installing a 58mm TB.

Lacking direct evidence, I'd say all this might cause is a slight deteriation to the idle quality. Nothing you'd be able to tell with a 248 @ .050 cam though.

That's not to say your IAC is functioning correctly.
But that would not make it run rich till 4k either.

I'd say in no particular order
vac leak
bad map
bad chip
bad injectors

Just because your chip guy says he does chips for your cam. Doesn't mean he really does. Or that he in fact sent you that chip. Mistakes do happen.
Get a cable and log what's going on.
Your going to have a hard time with that cam otherwise.

rooster433

I've been working with him lately and we have found a few things pretty far off.. slowly but surely its getting there.

First the IAT or MAT was left unplugged.


I got a datalog and we found the TPS was bad (reading 4.6 volts the entire time). I also noticed the IAC counts where at 160 at a 800rpm idle so I had him open up the blades a bit to get them back in check around 25-35 at fully warmed idle.

The final thing we are having a problem with is setting the base timing.. He says it won't run anywhere but way off the timing marker. Sounds like hes reading a ATDC or the pointer is a bit off... or a mixture of the two.


Just thought I would share.. you see post like this alot of times but hardly ever see the solutions.. Might help someone later down the road you know.