I've seen this topic touched on in other threads but never specifically addressed.

My '89 cranks over fine, 40lbs+ of pressure on the fuel rail but refuses to start unless I give it a shot of starting fluid in the intake. Runs fine until I turn it off and need to restart.

I have seen some knowledgable folks discuss the VATS system as a culprit as it locks out the injector pulse but Im pretty sure that a shot of staring fluid isn't going to restore the ECM sending the pulse.

Any insite from those wiser than I would be appreciated.

 

This has nothing to do with VATS.

Do you get any codes when it runs? Does it run rich or lean when it runs?

I would suspect the ignition system. How strong is the coil? What is the condition of your plugs and wires?

 

The fact it runs with starting fluid means it's getting spark. The fuel pressure shows it's got fuel...are injector pulses getting to the injectors? Is the oil pressure cut-out working properly? (It won't run if it doesn't detect oil pressure)

Got a Factory Service Manual?

 

I have noticed that the oil pressure as displayed on the dash has been running very low (20-30lbs at idle once engine is at operating temp). Sounds like
I should investigate this further.

 

That's not out-of-line, depending on temperature, oil, and vintage of motor.

 

The ECM will cut the injector pulse if it sees less than 10 or 5 psi of oil pressure if i remember correctly. So you should be ok

 

Bad vats means no starter crank.

 

VATS cuts off the starter relay and the injectors. If it cranks, VATS is OK (unless somebody bypassed the starter relay, in which case this is not a valid test). The ECM will not turn on the injectors if the VATS test fails, so that is not the issue. VATS failure will set error code 46.

The fact that it does run fine after you get it started tells us that fuel pump pressure, injector pulses and ignition are all good.

The ECM does not have an oil pressure input, so that is not a factor.

You said you have ~40 PSI of fuel pressure. Is that before starting or while the engine is running?

Could be a problem with the fuel pump relay. The oil pressure switch bypasses it when it sees about 6 PSI of oil pressure, which it would after starting with a shot of starting fluid. The ECM turns it on for 2 seconds at key-on and then after it sees reference pulses from the distributor. The engine wouldn't run without the reference pulses, so they are OK (they are used to synchronize the injector pulses). It just seems like the ECM-fuel pump relay part is not working as it should. That's why I asked above if you have fuel pressure before starting.

 

Cliff,

Great info. I did a little test overnight by leaving my fuel pressure gauge attached overnight. This morning it had 0 lbs. Now I'm not sure if it's my $45 Auto Zone gauge bleeding off pressure or more likely a leaking injector.

If I turn key to on, the fuel pump does charge the fuel rail up to 40 lbs.

I can see how a shot of starting fluid would overcome the few seconds it takes for the pump to charge the system. What baffles me is I can let the car run for 20 minutes, turn it off and immediately try to restart. No go without another shot of fluid.

 

perhaps the leakdown has gotten worse.Isnt there a sorta check valve to keep pressure and not let it return to the tank?( when off) Leaking injector would do the same i suppose.

 

leak down is not going to cause hard to start F there is 40 psi at key ON.

Look at the fuel test gauge when cranking. You should see the needle bounce while cranking IF the injectors are firing during cranking.If you do NOT see this, then your inj are NOT pulsing.
Go back and clean the dist wores, the tach wire, and coil contacts. The dist has to send reference pulse to the ECM for the inj to fire. VATS can still lock out the inj if the fuel inj side of the VATS is faulty. You can bypass the starter side of the VATS module but the inj side will still cut off the inj...that cmes back to seeing the inj pulse as it cranking. If there IS a inj pulse shown by the test gauge needle flickering...then the problem is ignition, or in the injectors themselves.

Don;t use starting fluid in an engine that has aluminum pistons and heads....Ether is for DIESEL engines. NOT gas motors.

 

Sounds like the fuel pump relay and circuit, needs attention.
If you supply 12v to terminal "G" on the ALCL connector, will it start ?

 

There is a check/pressure relief valve inside the fuel pump that will leak. Also the fuel pressure regulator leaks. In my personal opinion, as long as the pressure doesn't go down to zero in 5 or 10 minutes you're OK (some may dispute that time frame). If you have a leaky injector you'll have other problems. When the fuel pump is running you'll have adequate pressure, which is the important part.

The main thing is to have sufficient fuel pressure ALL the time, which includes key-on, cranking and running (especially WOT). The only way to know is to hook up a fuel pressure gauge and monitor it during all those conditions.

 

Something is not right .
The Aeromotive reg on my engine holds no rail pressure at all with the pump off and the engine always fires
straight up as soon as the OP switch runs the pump and repressuizes the rail while cranking over

 

VATS only shuts down the injector pulse while cranking over so the starter fluid OP sprays in would bypass that
lack of fuel and allow the engine to fire up?
You have fuel and spark, the engine fires up, you release the key , the ECM is getting the dist ref signal
so the injectors are fired (VATS is no longer in action ) and the engine continues to run

 

I don't see a FP relay issue at all. it primes, runs for 20 mins. oil pressure switch is not part of the problem, nor the soution. it is in parallel with FP relay, remember? both would have to fail, intermittently, to cause such a fuel starvation issue.

you didn't indicate if it fires and runs "clean," or struggles, sputters. does any one plug fire, or no spark? if plugs are wet from a leaking injector, I think the start fluid would fire the engine. if you suspect that, you can WOT while cranking.

I have seen a "no start after shut off" issue several times on the forum, some were ICM, coil, or pu coil, some were leaking injector or over rich, whatever. some disappeared after OP changed out everything!

won't hurt to disconnect TPS to see the reaction.

 

True, I failed to elaborate and dive into that deeper..

During cranking as you know the VATS might lock out the injectors and IF that were the case there would be NO fire with starter fluid sprayed in...it might fire but it would not continue to run because VATS has the inj locked out.

Another scenario would be a bad signal to the ECM...from the dist during cranking. The ECM is looking for a "run" confirmation via the dist. IF that were the situation then getting the thing to lite up would allow it to continue to run since the cranking has ended and the dist signal has sent the OK allowing the pump to run.
I think the mistake most folks make in diagnosing this kind of problem is assuming that the inj and pump are related...they are NOT. The inj are a separate system as is the pump. The pump can run but without inj cycling it does not matter...no ablilty to let the engine run. The inj can cycle but with no fuel pressure the eng will not run.

I can watch my 42 psi from 'key-ON' drop about 4 psi at a time during cranking as the injectors cycle with each eng revolution. They continue to use that "pretension" or stored/prime fuel pressure until the engine lites. The instant the engine is turning over on its own the fuel pressure returns to its preset range..in my case mid 40s since it is now sending the ok to the pump to run.
The injectors will cycle unless VATS has them locked out..its the pump that gets cut thru the cranking cycle until the engine runs. If the inj are NOT cycling during cranking that is a VATS issue. Because I have my VATS starter enable bypassed, I can still get VATS episodes but its fuel inj only. I can crank all day and the system will not allow run because there is no inj cycling. I learned to see the difference watching the fuel pressure test gauge when cranking...the needle moves with each inj pulse and uses that stored fuel pressure from the 2 second key on prime.

 

How so ....?
By spraying in the starter fluid in you have completely bypassed the non firing injectors as a means of supplying fuel ;
engine will run until the fluid is used up ( assuming spark available )
and as I previously noted ;
should you release the key from the cranking position while the engine is running on the starter fluid then VATS
turns off and the inj pulse would become active so the engine would continue to run until switched off again

 

Man, was I a sleep. Looking back at this thread, I see you have fuel pressure posted in the first post.

Maybe a problem with ignition switch. Do you loose 12v to injector fuses when ignition is turned to "Start" ?

 

I think you have to check to see if the injectors are pulsing. If you can confirm it with the fuel gauge flickering and using a noid light on one of the injectors that would narrow it down some more.

Gary