what do most ppl go with when it comes to your alternator. My 91 5.0 idles for a minute then starts.. then refuses to start back up it just rolls and rolls.. im thinking it may be the alternator as the fuel pump seems to be working.

I would like a chrome alternator but at the end of the day it doesn't really matter.

suggestion? is it possible its not the alternator and is there a way to test them?

 

alternator is not the problem as long as volts are above 13 while running.You need to find out if spark,fuel pressure,or injector drive is lost when the stall occurs-faulty ICM in the distributor is one of the more common causes for stall after running for a short time-next on the list would be fuel pump,then a list of about a dozen other items...

 

Suggestion? Yeah - fuel injectors.

GD

 

thats the thing.. i don't think the battery charges to 13... but i will have to check again... how can i tell for sure if its the injectors or the distributor.. any suggestions on a good brand name replacements?

 

It wouldn't matter - even if the alternator was completely dead it would not give the symptoms you describe. And as long as the alt is above 12.6 at idle, and off-idle it comes up to 14.5 or so then it should be good enough to run.

If the battery has enough volts/amps to turn over the engine then it should run regardless of whether it has a working alt or not - it would run till the battery died and at that point the battery would be too low to even crank the engine. The alt has nothing to do with making the engine run - it just charges the battery and provides electrical power so the battery is not depleted while running.

GD

 

still got the same problem... car rolls and rolls .. .then eventually starts and only stays running for a short time with driver assistance until cutting back out.

the car is flashing a code but i don't have a reader to check it.

 

still got the same problem... car rolls and rolls .. .then eventually starts and only stays running for a short time with driver assistance until cutting back out.

the car is flashing a code but i don't have a reader to check it.

 

As I said - injectors. Watch this series on the late RP Multecs and how they fail. You can check the injector coil resistance with a meter. Eric on SMA is excellent with a scope and there's two parts to this series.


And you don't need a code scanner. Read through this:

https://www.freeautomechanic.com/dia...blecodes5.html

Multec failures are par for the course with this era TPI system.

Might also be a bad fuel pump. That's also par for this course.

GD

 

looks like there is fuel around one of the injectors

 

Well that's not ideal. Check fuel pressure at the shrader on the passenger side fuel rail, and check coil resistance on the injectors.

GD

 

I was 45 minutes out from home and my alternator died. I drive it all the way home on battery alone.

 

a local mechanic dropped by my house and told me the injector needed replacement. so I went on rock auto and got one.. I will let you guys know what happens when I install it.... do you guys have recommended brands for a 5.0 tpi I know at one point ppl used to use mustang injectors.

 

You should probably replace them all. Get Delphi injectors from South Bay Injectors (forum sponsor).

GD

 

i will take a look.. does he ship to canada.. i got the 5.0 tpi

 

Have to ask them. Not sure on that. You need the 19 lb Delphi injectors for a direct swap.

GD

 

should I take the time and upgrade my injectors to higher lbs? does it make a difference in hp ? because I do plan some upgrades for the GTA once the car is repaired.

 

That's a whole different kettle of fish. Now you're getting into tuning and burning custom chips, etc. You can't just upgrade the injectors without tuning the computer. And no - it will make zero difference in HP. The engine is an air pump. It just happens to mix the oxygen in the air with fuel for combustion as the driving force. Unless you get the engine to pump more AIR (not fuel), the performance stays the same. Larger injectors without tuning will confuse the computer and make it run worse.

GD

 

can i just change one injector.. i know most ppl say to change them all but i can see the faulty one i just don't know if i can remove it without removing the runners and the fuel rails.

 

You need to remove the runners. You should really replace them all especially if they are multecs.

 

yeah i was afraid u were gonna say that. thanks.

 

It's way too much work to do just one. You can do whatever you like but Multecs are junk at this age and replacing one would be foolish.

GD

 

yeah i figured as much.. i know most ppl go with the bosch or delphis... which ones do u recommend? i may as well replace them all as the garage will have to do it.. im guessing at least 3 hours to change them all

 

The Delphi’s will be a more of a direct replacement and shouldn’t require tuning.

 

delphi's at southbay have a steep price tag.. anyone have experience with the bosch injectors with the adapters?

 

These Bosch 2 should be a direct replacement without tuning as well.
You can always ask them and use tg11 discount code at checkout.
https://www.southbayfuelinjectors.co...tors-1985-1992

 

The Bosch 3s are a great injector but you need to change the battery voltage offsets in your ecms tune.

 

are these injectors remanufactured?

and with the bosch 3's what ecm tune would i need? so i would have to buy a new tpi chip?

 

Yes they are remanufactured . For the tune you can but a moates.net burn2 and a sst27sf512 eeprom and a g1 adapter.
Its very easy to change your calibration. For your car you might want to use axxb.bin
http://www.gearhead-efi.com/Fuel-Inj...Information-8D

 

I bet if you did an injector balance test you would find a couple of the other 7 are off also.
My car was running extremely rich. Removing as much fuel as the computer would allow. I think an idle BLM was like 108, or whatever the bottom is. So I measured each injector. 3 on the drivers side had a pressure drop of 20 psi (on 30 pulses if I remember) and 1 went all the way to 0. And the O2 sensor is on the drivers side so that makes sense. Over on the passenger, 3 dropped 20psi, and 1 dropped like 5. So running lean on that side. So just replace all 8 and be done with it.
I guess I was lucky because after replacement and driving around for a week, I had perfect fuel trims, no chip burn needed (although I did anyway for EGR). Maybe you wont need a burn either. But if you do, its easy to do with moates hardware and software.

 

My car won't even stay goin at this point.. it rolls and rolls then starts.. I keep the gas to it but I get about 30 secondo to a min and it cuts out... I wonder if I put her in gear if she wud stay goin easier.

 

If it’s in gear there is more of a load on the engine. Are you still messing around with the old injectors ?
what do the ohm out at ?

 

no im not actually, i was gonna try to put her in the garage which is about 100 feet away bc im goin out of town. Im ordering new injectors for her today from southbay and i do have edelbrock valve covers to go on her.. so that may be the perfect time to install them..,maybe?

 

I have changed out the injectors for a set from south bay... car still won't start... fuel pump seems to be kicking in.. not sure if it cuts out after or not.. but it does have power.. garage is now doing a fuel pressure test to see if the pump is pumping enuf fuel.

 

Any updates?

 

Not yet.. I shud know more tomorrow

 

recently replaced factory with delphi. car fires up as soon as key is turned. couldn’t be happier. also bought new alt to get by until proper restore of factory can be done. got acdelco reman. made in mexico. works like a champ. only thing i don’t like is the color

 

garage didn't have time to do the pressure test on the car... now waiting for wednesday or friday to get it done... i might get a new ignition switch just to be safe althought im not sure thats the issue.. its really confusing.

 

still waiting on the garage guys... I'm getting a little irritated.. but I gotta wait as I don't want to have tow the car to another garage. I'm leaning towards the fuel pressure... as the pump does indeed cut in... I changed the fuel filter when I purchased the car in 2015 so I don't think its that.

so besides the pump wat else would cause low pressure.. I'm sure theres a sensor somewhere that I haven't changed.. and does anyone know what pressure the pump should be at?

 

There are no sensors that affect fuel pump pressure. It is mechanically regulated. A filter changed in 2015 doesn't mean much - a dirty fuel tank can plug a filter in a few minutes, days, or weeks. Fuel pressure should be 43.5 psi.

 

I think I would buy a fuel pressure gauge and go test it myself in their parking lot if it takes them that long to do a fuel pressure test.
So you have the new injectors installed? You say the fuel pump kicks on but does it kick on to prime when you turn the key from off to run (not crank)?

The reason I ask is years ago I had an issue where my car wouldn't crank unless I spun the starter enough to build oil pressure. Why does this matter there is two ways the car turns on the fuel pump. ECU signal and oil pressure switch. So if the ECU signal isn't occurring starting the car for several seconds cold will build enough pressure to kick in the oil switch control. But with warm oil you typically can't build enough pressure on the starter to trigger the oil switch.

Out of curiosity have you tried bypassing the fuel pump relay and see if it cranks more reliably. Also look at the wiring around the relay its not too uncommon for it to over heat and melt the wires at the relay.

 

the bosch injectors from southbay have been installed.. no change in the car but the injectors had to be changed anyway as one was leaking. and with the ignition to on without rolling to start the car I can hear the pump in the tank fire up.
when I changed the fuel filter.. I just bought a cheap one from my local Canadian tire.. I believe he was 7 bucks or something like that so I will change him again to be on the safe side.

UPDATE: I found a receipt in the car and it looks like the previous owner had the full ecm changed? I have not heard of someone doing that and I am worried maybe the ecm is acting up again?

 

I dont think swapping out an ECM is that uncommon. Both Z28s I have had both had an ECM swap at the dealer. I dont know if there was a recall, or they just eventually died. Even the car I have now thats roughly 80k miles had it replaced.

 

Out of my three cars I have pulled the ECM from - two had replacement units. And my 86 that didn't - the ECM was bad. Many of these had issues with circuit board or solder joint cracking.

GD

 

UPDATE:... pump is fine and working properly... however.. the injectors are NOT firing... mechanic gonna take another look on Monday

 

yeah we went ahead and changed all 8 with a set from South Bay.. however the injectors aren't firing and were not sure on the cause as of yet,

 

mechanic figures it down to the ecm... im gonna order one from rockauto this week

 

Summit has a good price on the 1227730

https://www.summitracing.com/parts/aaz-77-7730/