'87 Camaro Z-28 Fuel problems? Help!

[Falkor87Z28]

Hi Im new to the site, and really dont know much about cars in general. Im quite young and willing to learn. I bought my first car about a year ago maybe, a black 1987 Camaro Z-28, 8 Cylinder Tuned port injection engine. Sorry i dont know much more about it.

If you dont feel like reading the whole thing, ive got this camaro, cranks/turns over, wont fire/catch unless starter fluid sprayed. When it does it just catches and fires for a brief second, doesnt start still. fuel pump? injectors? i havent got a clue here, stumped a mechanic and my father.

I was turning onto a road one night, when accelerating into 1st the car just dropped out, I lost power steering, the pedal went to the floor because I lost all pressure there, I lost all power to do anything, I had to dive into a drive way and slow down quickly. I left it on for a good minute listening to it, it was running like a lawn mower, really crappy and hardly at all. Lights were on on dash, radio was working, headlights were on, everything electrical works fine. I started it once more after cutting it off, it fired and ran like a lawn mower again. After letting it sit a few days we towed it back, and began checking it out.

Now it wont start at all, it cranks but unless we spray starter fluid we get no fire. We've cleaned the fuel filters and changed spark plugs, to rule things out. Im thinking fuel pump? injectors? I really dont know much, and im desperate for some help.

please help me out X_X I dont have much of a clue so if you could keep that in mind that would be great I can follow instructions real well and im willing to learn anything it takes. if you know anything a mechanic would be able to understand I know one that has checked it out and another that is going to soon, both family friends. Thanks a lot and sorry for the long post.

[89IROC&RS]

you said it started to sound like a lawn mower, i think thats your key symptom.

first things first, check your check engine codes. you said you had that come on before with similar symptoms but it went away. take a paperclip and wire the top two ports on the right hand side of your DLC together, count the flashes from your check engine light and write them down.

with what youve written my guess is you have an oil pressure problem. either your oil level is low, or your pump is bad, or the pressure sensor is bad. the computer is setup so that when you have no oil pressure, it cuts fuel to the engine. the "lawnmower" sound was probly the death crys of your valvtrain

-e

[FormulaLT1]

Holy crap , did I take up smoking crack again or am I actually looking at a new 89iroc&rs post?

[Falkor87Z28]

Again? lol, Well I sent him a PM I dont think we've even checked anything regarding oil. As soon as I can ill check the codes for you and tell you here. Also now that we've towed it home, it doesnt want to start at all, no lawnmower, no nothing. It turns over/cranks but doesnt catch, no fired unless starter fluid is sprayed. Thats the current condition. Ill add what you said to the "Things we think might be wrong" list and get to work on checking them out.

[Blue Bowtie]

Originally Posted by 89IROC&RS

... the computer is setup so that when you have no oil pressure, it cuts fuel to the engine. the "lawnmower" sound was probly the death crys of your valvtrain -e

Not to start any disagreements, but merely to set the record straight, I must disagree with that theory.

First, the only link between the ECM and auxiliary oil pressure switch is the fuel pump voltage input on B2. That input is only used to determine fuel pump status, and there are no analog outputs to control fuel pressure.

Second, disassembling the binaries for the ECM reveals that the programming and firmware merely monitors the fuel pump voltage. It cannot alter it other than to shut off the pump relay ground. If the oil pressure switch is closed, that makes no difference. The only thing the ECM can do to stop fuel is cut injector pulses, not the pump relay.

Thirdly, a quick look at the schematic reveals that the oil pressure switch is wired in parallel with the fuel pump relay, NOT in series. Therefore, there is no way that the oil pressure switch can shut off teh fuel pump is the relay is energized. The relay will remain energized as long as there are distributor reference pulses being reported to the ECM. Therefore, the ECM will recieve signal on B2 so long as the relay OR the switch is providing power to the pump circuit.




Don't feel bad. This is a common misconception being propagated around the industry as a result of a basic lack of understanding of the system. The auxiliary oil pressure switch is NOT a "safety shut-off" but merely a redundant path for pump power in the event of a relay failure. This misconception is likely the result of assumptions made about the system rather than studying it. The misconception is probably reinforced by the fact that Ford DOES use an inertial fuel pump cutoff switch, and the presumption that GM uses a similar system. As of this writing, NO domestic GM vehicle uses a fuel cut-off switch.

Even some technicians at dealership service departments will argue until they are blue-lipped that the oil pressure switch will cut off fuel. That's just how misunderstood the system really is. That works until you walk over to a running EFI engine and pull the wire from the switch, and the engine continues to run until the tank is empty. Try it on your own vehicle if you doubt it.

As for the initial question, I would agree with 89IROC&RS and suspect that the problems described are related to fuel pressure or delivery. It's just that the oil pressure switch has nothing to do with that. If you can manually administer fuel to get the engine running briefly, you are obviously not getting fuel through the traditional routes.

[89IROC&RS]

YOURE MY BOY BLUE!!!!!

sorry, it had to be done.

interesting though, im not 100% sure about the fuel cutoff on the third gens, neither of mine are running right now so i cant do the plug removal.

however i was a line tech, working specifically on electronics and driveability, and had several occations where the corvettes i worked on would not run due to a bad oil switch. so be it by cutting power to the pump, or to the injectors, lack of oil does in one way or another cut fuel to the engine.

but like i said, that system may or may not apply to the third gens, im not sure.

although on the flip side it is fantastic to see another person with tech experience that is also a mod. welcome blue.

-e

[89IROC&RS]

and geezus christ formula, ive been gone how long and you still havent out posted me???????

and blue nothin but love for ya, but damn formula, not even a thousand posts and hes a mod

[FormulaLT1]

Originally Posted by 89IROC&RS

and geezus christ formula, ive been gone how long and you still havent out posted me???????

and blue nothin but love for ya, but damn formula, not even a thousand posts and hes a mod

I had my post count edited down so I wouldn't look like such a sloppy whore . My actual count is over 10K or so. Blue is a welcome new additional, he has well over 8 or 9 + years of modding experience at a very popular F-body site (I won't mention the name of the forum cause of our advertising rules) and also has personal experience with many GM (hense why he was added to all of Chevy).

Its good to see you pop your head in though 89, I almost had to do a double take .

[goldz28]

I agree it is nice to have someone with lots of experience and the ability to pull schematics out of places we really don't want to know...

[Morley]

Try checking your inj1 & inj 2 fuses on the fuse block. If they are good, get a noid light and hook it up in place of one of the injectors. While someone cranks the car, watch the light. If it pulses while cranking then the ECM is commanding the injectors to fire. If the light isn't pulsing, then the ECM isn't seeing the refrence pulse from the distributor. This comes from the ignition module, located in the distributor, under the rotor. Only use AC Delco modules, or you'll be replacing it again soon. If the noid light isn't pulsing, start by checking for continuity on the ref pulse wire and check it to ground to make sure it isn't shorted. If the wire checks good, try an igintion module. If it still doesn't fire the injectors, try another ECM.
If the light is pulsing, check your fuel pressure, if the pump is running and the pressure is low or zero, the filter may be plugged or the pump is bad. If the pump is running and you have good pressure and the noid light pulses, probably bad injectors. Ohm them out across their terminals. They should be around 15-17 ohms, anything much higher or lower indicates a bad injector.
If the injectors all check out good and pressure is good, check for fuel in the vacuum line to the regulator. If there is fuel in it, the regulator is bad. If the pump isn't running when you first turn the key on and never turns on when cranking the engine, check the relay AND oil pressure switch. If both of them are bad, the pump won't run. The relay is supposed to prime the system when the key is turned on then run once the engine cranks over. If the relay has failed the oil pressure switch is supposed to close at around 7 psi and power the pump (it does this with the relay working or not)
This about covers a no fuel condition.

[Blue Bowtie]

89IROC could be correct.

I haven't pulled the diagrams for the C6s yet to confirm it, but I did find the AllData schematics for the C4 and C5 Y-Bodies. Neither of them show an oil pressure switch anywhere in series with the relay in the fuel pump circuit.





They DO show the oil pressure switch in parallel (by default, since it isn't in series) on teh diagrams.

I suppose it's possible that they are mistaken - It wouldn't be the first time. And it's possible that the C6s are different.

[wyotech87z28]

Well it sounds like these guys pretty much have this problem whipped...if I remember right if you look in the wire loom near the firewall where the harness comes through (just to the right of the brake booster) there should be a single red wire with a male spade connector on it....this is the fuel pump primer wire...if you put battery voltage directly to this wire it should make the fuel pump run bypassing the relay. This would ensure that fuel pump itself is on. Just because it turns on doesn't necessarily mean it is operating normally, you should definitely do a bucket test and pressure tests to ensure proper pumping. Also consult wiring diagrams and check the neccesary relays. Obviously the first checks would be using a spark tester to see if you have spark on the secondary side of the ignition coil (at the spark plug) and putting a noid light on one of the injectors connectors. The injectors on this model along with many others are controlled on the ground side...so if you unplug an injector with the key on you should have 12v (source voltage) on one side of that connector constant. From the condition you explained it very well could be an ignition module fried (not an uncommon problem with GM vehicles) which is underneath the distributor cap. If the transistor in the module burned open you will not have any spark, and if the hall effect sensor in the distributor is malfunctioning you may not have spark or injector pulse bc the PCM uses this sensor to detect engine RPM to adjust ignition coil dwell (on time) and fuel trim (injector pulse).