Sat For 20 Years...Need Help With Diagnostic For Rough Running / Stalling (Page 2/6)
CampyBob JAN 10, 05:51 AM

quote
Originally posted by RandomTask:

Did it sit with gas for that long? When I revived a 85 a while ago, the fuel hose that was in the tank from the pump to outlet turned to mush from sitting so long. May be something to consider.



It started out in 1999 with a full tank of gas. That must have gradually evaporated down to the 1" or so of stinky varnish crap that I mentioned above. All fuel lines were in good shape. I replaced the fuel pump pressure line (rubber) that ran from the sending unit to the line that takes the gas up to the throttle body because I had to cut that one to get it off the steel line. It was maybe 6" to 8" long and other than being stuck fast onto the steel it was in good shape. No lines were soft or mushy. New hose clamps were used everywhere even though that was just a precautionary move.

The old fuel pump looked good, felt good (not soft or deteriorated), but it was obviously not pumping so replacement was a no brainer. I have no means of checking the output pressure, but as I said above the flow rate 'looks' darn good with the fuel line disconnected at the throttle body and just running the pump and allowing the gas to to shoot into a catch can in the engine compartment. The 4-holer fuel pump only specs at 13 PSI so basically a very low pressure system.
CampyBob JAN 10, 06:09 AM

quote
Originally posted by Patrick:

Bob, I discovered that my '84 wouldn't run properly with 4 psi of fuel pressure. The symptoms I was experiencing were somewhat similar to yours. If you wish, you can read about it Here.



Very interesting.

I suspect this is also my problem as I also get no flow on the return line to the tank. I will drop the tank again and inspect the pump mounting, the hoses inside the tank, replace hoses and add hose clamps as required.

I've said all along to myself and anyone near me that would listen that the engine bogging, stuttering and not revving sounded like a fuel starvation issue. I did not think any of the sensors just deteriorated over the 20 years the car sat, but when I got the code 22 I replaced the TPS per the Fiero Store tech page instructions.

So, basically you guys are say I MUST have a return flow into the fuel tank in order to have enough PSI at the throttle body to properly feed the engine with enough gas? As I said earlier there has been no return line flow back into the tank. I will pressure test the output line if I can buy a gauge and adapter setup, but your analysis sounds like it might be my problem. And yes, the pump I installed is a Chinese Autozone $30 unit. The filter sock might also be coated with freshly loosened 'crud' that was still in the tank also.

I think a pressure test and tank drop are in my future. Thank you, sir!
CampyBob JAN 10, 06:18 AM
[QUOTE]Originally posted by fierosound:

Welcome!

After sitting 20 years any number of things could be bad.
But you've already covered most things in the fuel system.
And the engine will run...

Is Check Engine light on? Any new ECM codes?
http://www.fiero.nl/cgi-bin/main.cgi?ECMCodes

ECM uses MAP, TPS, CTS, and IAT (? 85 Duke) inputs for starting/idling. O2 input once sensor is hot.
MAP is affected by leaks in vacuum lines. Check all of those.

Coolant Temp Sensor (CTS) may have gone bad.


I had a CTS go bad on my '88 Cherokee and that caused a massive raw fuel dump and flooding to the point the engine would not even start. I will look at replacing the Fiero's CTS, but I don't think it deteriorated from sitting as I pulled it and the tip looked good. Never know until a voltage / resistance test though.

Will double check for vacuum leaks. None found to the MAP sensor so far or the EGR or anywhere else I went poking around.

No CEL and the only other code trip was when we disconnected the MAP sensor. Today I'm swapping in another MAP sensor and checking out the IAC, but I think a fuel pressure test and possible fuel tank drop is in my future if those don't fix the stumbling, stalling, lack of revving, etc.
wftb JAN 10, 11:27 AM
An easy way to check fuel flow on an 84 2.5 is to take the air cleaner top off, get the car idling and rev it up by hand. If you don't see a huge increase in the gas flow pattern then you have a problem . My 85 had the rotten tube from the fuel pump up to the hard line, same as someone mentioned above. I have not seen any mention of the fuel pressure regulator but if you have no gas going out the return line you should check it.The problem might be too much fuel as opposed to too little fuel.

------------------
86 GT built 2.2 ecotec turbo
rear SLA suspension
QA1 coilovers on tube arms

sledcaddie JAN 10, 11:40 AM
1988 GT 2.8, 5 speed. If rough idle, low power is an issue, wouldn't it throw a code, indicating which sensor is bad? Is there a code for a plugged injector?
Patrick JAN 10, 12:32 PM

quote
Originally posted by CampyBob:

I will pressure test the output line if I can buy a gauge and adapter setup...



I didn't bother with an adapter.

Some automotive supply stores have fuel pressure testers you can borrow.


quote
Originally posted by Patrick:

I disconnected the fuel filter (it was very clean inside) and connected a fuel pressure gauge onto the end of the fuel supply line. I then jumped terminal "G" at the ALDL connector with 12v from the cigarette lighter to run the fuel pump. The gauge showed a grand total of 4 lbs pressure while the pump was running, and immediately dropped to zero when the power was cut.
Gall757 JAN 10, 12:36 PM

quote
Originally posted by sledcaddie:

1988 GT 2.8, 5 speed. If rough idle, low power is an issue, wouldn't it throw a code, indicating which sensor is bad? Is there a code for a plugged injector?



Are you in the right thread?
fierosound JAN 10, 12:45 PM

quote
Originally posted by CampyBob:

... but I think a fuel pressure test and possible fuel tank drop is in my future if those don't fix the stumbling, stalling, lack of revving, etc.



SO annoying to have to drop the tank again after you just replaced the fuel pump.
Joseph Upson JAN 10, 03:52 PM
I don't recall, but if it's possible to look at short and long term fuel trims for this OBD I system that should give a good indication as to whether it's leaning out, or flooding. I had a bad MAP sensor in a Fiero once that never set a code. It locked at a value just below part throttle and would idle and take off fine up to about half throttle and then fall over beyond the locked value as if a light switch had been turned off.

Someone here may recall the condition/circumstances, but I believe if the ALDL diagnostic terminals, A,B are grounded together, the engine light will flash at a frequency that corresponds to whether the fuel condition is rich, or lean with the motor running, as the rpms are raised a bit.

[This message has been edited by Joseph Upson (edited 01-10-2020).]

Gall757 JAN 10, 05:17 PM
Code 44 is 'lean', and Code 45 is 'rich', but it's not foolproof..based on oxygen sensor readings.