one of my friends 90 rs with a tbi is having problems in having his motor runing after we swap the old intake for a new oem one. we already changed the injectors, fuel regulator, fuel pump and filter, ignition coil, module, tps, cts. We know it has spark and we know the distributor is not 180 off, the motor turns and it injects fuel into the tb fuel lines arent kinked, all fuses check out good we tried another distributor because we thought it was the pick up coil and still didnt turn on what else can possibly be wrong with this motor if all we did was swap the intake manifold!! the last thing i can think of is a bad ecm or the timing chain is off is there a way to diagnose a bad ecm or a bad timing chain? please help! its my friends daily driver

 

TBI are very simple systems and generally well behaved. However swapping manifolds leads to base timing being disturbed.

In your friends case, since you have spark and both injectors are spraying (please confirm this) fuel during cranking and you have no ignition what so ever the most common cause is the incorrectly routed spark plug wires or incorrect #1 cylinder post on dizzy.

1) Pull all plugs to make your job turning engine easier.
2) Get a breaker bar and turn engine by hand CW.
3) Get a giant straw from 7-eleven and insert into #1 Cyl
4) Turn engine CW slowly until you balancer timing mark aligns with TDC. The straw should be popping out as piston is nearing TDC, both cyl #1 valves should be closed and #6 cyl should be rocking.
5) Turn engine with breaker bar about TDC (CW and CCW) and poke with a straw to make sure that piston is at or very near TDC.
6) Pull dizzy hat off and use straight edge to mark position of rotor when cyl #1 is at TDC on dizzy body. - Compare to your previous #1 Cyl post and make appropriate adjustment (twist dizzy, and or re-route spark plug wires)

If you are getting injectors to fire during cranking the chances are that ECM is 99% functional. Also, turn ign key from off to run position without starting - SES should light up blink off and remain solid. If you get that that means ECM past POST test. During this test Fuel pump should turn on for about 2 to 3 seconds and shut off. Furthermore, get a paper clip short pins A&B on ALDL connector - SES should blink code 12 which means that there are no stored fault codes.

To check timing chain requires valve cover removal - observe rocker arms when cranking engine.

//RF

 

Wouldn't it be less work to open the dizzy and verify rotor is turning?

 

well we rechecked the routing of the wires as well as the firing order and all wires are in place, second i put my finger on #1 spark plug hole while my friend bump the key as long as i felt compression he stoped and turn the motor manually to TDC and the rotor was pointing straigt at #1 cylinder. i checked the ecm with the jumper and it gives a code 12 so the ecm is good and it doenst have any codes stored in it, so what the heck!!! im going crazy with this tbi nightmare lol

 

Yes, that would give an indication that timing chain is still there, but you can not tell of jumped couple of teeth. Looking at the rocker arms gives an indication that valve timing more a less there. Dizzy spinning should be easier - agree.

 

I would put in a fresh set of plugs then use some starting fluid to see what happened. If it doesn't run right still I'd go back and verify the distributer is 100% correct. It is very common to install them 180* out because there are two TDC's.
I assume you have eliminated most other possibilities like a large vacuum leak (power brake line) and/or disconnected wires to sensors.

 

thanks for the replys. i was wondering if theres any other way to make sure the dist is at the right TDC i even put a piece of wire with a 90* tip inside the plug hole and i can feel the piston. i will get fresh plugs and we been using starting fluid since the beginning. we double checked all sensors and hoses is there any critical sensor that will make it not start? also one thing i notice is while the motor is turning it dont read no oil pressure even though theres oil in it, would that make the ecm dont start the motor

 

The exhaust TDC fools a lot of people. I always pull the valvecover and watch the rockers to make sure it's the right one. Both valves will be closed, but with the correct TDC the valves will also be closed as you are turning the engine to approach the TDC mark (turning it clockwise how it runs). With the exhaust TDC the exhaust valve will be closing as you approach the TDC. Just watch it for about four full turns til you're positive.

If you had the oil pressure cutoff you wouldn't get fuel.
The coolant temp sensor is a very important one for fueling, but it doesn't always prevent you from starting.

If you have been trying it for so long and using starting fluid then it's likely your plugs are wet-down fouled. You can dry them out with a propane torch cooking the tips for about 2 minutes each, or just grab some fresh plugs once you know the TDC is correct. Otherwise it may run pretty bad while the plugs are fouled.

 

spark plugs, that was it! you were right 350sbc they were wet-down fouled and they looked like they went thru some detonation but the darn thing finally starts it idles funny but we're about to adjust the tps. well at least we ended up with a bunch of new parts for the rs thanks for the help

 

Great you got it firing. I assumed this was a running engine before the intake swap, it should have started right up.