No start problem w/89 chev. truck (LONG)

[larry33kc]

Well guy's I have asked for help on this at the fullsize board to no avail, and it is driving me crazy so hopefully someone here can help with this

I have a 89 chevy 4x4 350 TBI

I just got a 55,000 mile crate motor that I installed and I can't get it to run right.

First off it will not start on its own without using starting fluid, it will just crank, and crank, and crank, wont hit at all. But if you spray S/F in it it will fire right up first hit.
It runs but has a miss and most of the time if revved to about 2500 rpm it will act like you just shut it off then will start to run when the rpms drop. you cant drive it at all it will just die. it does alot of popping and backfireing through the exhaust (open manifolds).
Once you have started it, and it has run it will fire right up first try every time unless it sets for a few hours, then you have to spray S/F in it again to get it to start.

Here is what I have done , replaced, and checked.

First off I have done a compression check, and it has fuel and spark

Replaced with new items, fuel pump soleniod, oil preasure switch, fuel filter, battery, plugs, plug wires, ignition module

Replaced with used or parts off of old motor, Stock 34,000 fuel pump from my GN, fuel tank, fuel sending unit, distributer, TBI (it had a Holley 670 TBI on it first from the old motor went to the stock TBI), I have switched IAC's

I have checked and cleaned all the grounds about a 100 times, even used jumper cables at different spots while running to check the grounds

It has only run right ONE time and that was after the TBI swap.
We replaced the holley TBI with the old stocker and after cranking it several times my Bro In Law said it shot a big load of fuel for the start, and was spraying alot more while running than the holley did.

It ran fine not popping or missing, it revved cleanly and fast sounded great. It did start hard but that was because we had just swapped distributers right before and couldn't get it to time because it wouldn't start if you disconected the timeing wire to time it so we set it bye ear with the wire hooked up.

Now that we thought we figured it out I disconected the timeing wire and set the timeing at 0 deg. reconnected the timeing wire and bam it started to run like crap again.

The truck had set for a few years and a guy told my BIL that varnish builds up in the fuel lines and plugges the injectors up, which I thought could happen so I go to the Holley TBI and pull the injectors from it because they just pop right out with no gaskets like the stocker, I was thinking that this is the problem and figured to see a bunch of crap on the filter but there was nothing, not even a little speck of dirt

I am lost with this thing and I am on the firge of takeing the sledge hammer to it. The 60 day warrenty is almost up on this thing also.

I am sure I have forgot some things, but please help if you can TIA

 

[87grandnational]

Honestaly, This IS a guess, but from the way your truck is acting i would say its getting way too much fuel. Is this Fuel Injected? Or Carb'd If its carbd take your carb off and make sure the float isnt stuck, (sometimes a stuck float will tend to make more fuel go into the cylindars, or so thats what would happend on my gokart) If its fuel injected. Check your Fuel pressure regulator, If you dont have one. get one. Does the truck have an after market Fuel Pump? A few things could me. Carb'd Stuck valve/float. Fuel Injected fuel regulator set too high? When i did an induction clean on my car. When i tried to rev it. It would try to die and then kick up higher. You could possably be getting too much fuel which my guess is as good as any others. so good luck hope this helps.

Anyway incase this doesnt work heres a bump for ya...

BUMP!!!!

 

[Drac0nic]

Get a fuel pressure gauge and hook it up. The TBI engines run at about 12-15 PSI. Don't worry about the pump, it'll work fine. The regulator will take care of it provided your system's in proper working order. The injectors should be spitting out a cone shaped stream of fuel, there shouldn't be any dripping from them. Otherwise I'm for busting out the timing light and seeing if everything's square there.

 

[Little6pack]

Does your truck have computer controls CC?
Does it have dual gas tanks? Maybe bad gas.
Why not toss the TBI & go back to what the motor had on it.
DID you listen or hear this motor run prior to buying it?

I just bought an 87 r10 chevy & the 350 is TBI.
Someday I am going to refresh this motor then put it in my son's Monte
When that happens I will run it the old fashion way with NO PUTER.

 

[larry33kc]

Well I don't have a fuel preasure gauge, but I now that every thing to the TBI is ok. From what my BIL says it spray's very little fuel to start, except when we switched out the TBI's then he said it sprayed a big burst of fuel to start, and was spraying alot more fuel while running.

After we got it to run fine I set the timing to 0 DEG. as per spec with the timing wire disconected. After running for a few minutes shut it off to see if it would restart ok, thats when it started to run bad again.

Yes it is computer controled
No it dosn't have dual tanks
And the motor is a TBI motor originally, I had a aftermarket Holley TBI on it (670 holley TBI) before, now it has the stocker
No I didn't hear the motor before but I did check it out and it check out fine, 150#+ comp. timing chain good, looked like it had 5000 miles on it instead 55,000, It also carry's 60+ pounds of oil preasure.

I am pretty sure we have narrowed it down to fuel but not sure why it sprayed fine one minute the bad the next, But what ever it is I am begining to think the old motor (388 stroker) that was in it wasssn't bad after all because this is what it was doing when it quit running before I parked it. It just started to gradually run bad till it wouldn't run at all.

 

[steve hughes]

Coolant temp sensor maybe out of whack. Put a scan tool on it. Is it reading the actual temp of the engine ? What about the o2 volts?. Is it showing rich or lean? If you have turbo link it will work on this truck.

 

[myclone]

As was mentioned make sure the coolant temp sensor for the ECM isnt bad as that could make it pig rich or WAY lean. Also, there should be a "clear flood" mode the ECM goes into after extended cranking so if you are having to crank the motor for a long time it could be going into the clear flood mode. If so youll need to depress the accelerator pedal while cranking. Last thing Id consider replacing is the ECM as they do go bad from time to time although pretty rare on these trucks.

If all the above check out then Id look REAL close at the the fuel system back at the tank since it fires right up with SF. If you swapped pumps you did put a new fuel sock on it, right? The original can start to deteriorate and the debri can plug up the pump. Make SURE the tank is clean too as any trash in there that can get past the fuel sock will kill the pump in no time. The wiring/connections in the tank as well as the connection at the top of the tank are problem areas on these trucks with burned up wiring, corroded connections, etc so look at that stuff closely. The last thing I can think of is the "pulsator" that supposed to quiet the pump when its running... These things are notorious for leaking which drops the FP below usable levels. Ive done 7 or 8 fuel pumps in these trucks and I toss the pulsator every time and replace it with a piece of high pressure hose and a couple of hose clamps. Its only slightly louder this way when the tank is close to empty but anything more than 1/4 tank it quiets down to where you can barely hear it.

Hope some of that helps and if it were me Id throw an ECM in the thing first cause thats the easiest to do of all the above (I never said I wasnt lazy )

 

[11.20n1320]

I would be looking at the MAP sesor hose at the TBI to see if it is at the correct port, and has good vac. supply.Also would be good to know what the ECT sensor is reading. Try starting it with the ECT unplugged. That will make the ECM think it is -38 deg.f.You should have a very large amount of fuel spray at the injectors.This should only be done to see if the hard start goes away.Also check the top of the coil tower for funk growing on it.

 

[larry33kc]

Ok guy's thanks for the responses here is what I got

I bought a fuel presure diagnostic kit and it showed 12#'s of fuel pressure with no fluctuation while revving, so I guess that checks out ok

The fuel sock only had 34,000 miles on it and was way cleaner than the one that came out of it which still worked fine, it was replaced to eliminate any problem with it.

It never had a pulsator on it from the factory it had a thick hose on it, which I replaced with a fuel line to eliminate a problem it that

all the wiring at the pump was good inside and out also made sure the grounds were clean, It has had 2 sending units in it also to eliminate any problems with it

The Map sensor is new and hooked to the factory port on the back of the TBI

I did disconnect the ECT sensor, and it did start right up, but still ran rough, I do have a new one to install later.

I don't have a extra ECM to swap and they seem a bit pricey with no way to return it if it isn't the problem, so I havent gone that route yet.

Also there is nothing growing on the coil and it is the second one that has been installed also to eliminate any problems with that

Still at a loss here looking for more ideas getting close to hunting season and I need my truck

 

[larry33kc]

Any ideas out there

 

[Drac0nic]

hey, if you need a spare box and it's the1227747 ECM I've got a spare I'll let go for $25+ship, I've had it in my Astro before, powered up fine. You'll need to supply the EPROM and cal-pack for the 350 though. ED:since it's OBD1, would a Scanmaster or some other diag tool work on it? I'm goin with WinALDL, so I'm not too up on Scanmaster's comaptibility. May be helpful.