Fuel/Ignition/Other? 4.3 CPI

[daveg_01]

Fuel/Ignition/Other? Please help

 

I have been trying to figure this out with no success. Can you guys take a look and offer any suggestions you might have?

 

 

Vehicle:

1995 CHEVROLET TRUCK ASTRO VAN

2WD Automatic Transmission

6 Cylinders 4.3L CPI

105,000 miles

 

Symptoms:

The van always starts and runs fine for at least a minute or two.

However after a short distance it will not accelerate properly and it will try to stall. As it progresses I might get some popping at the engine and eventually it will die. When I press the accelerator it acts like it wants to die.

 

It takes as much as 10 to 15 minutes of regular city driving to cause these symptoms or 2-3 minutes of driving under a load (when I hot-rod it). It does not seem to be directly related to engine temperature.

 

If the van completely dies, I can turn it off for 10 seconds then right back on and it definitely drives better (not completely normal). If I leave it off for 15 minutes it usually runs quite a bit better. Overnight and it runs normal when I first start it.

 

Parts Replaced:

Leaky CPI (spider)

Inlet outlet fuel lines (nut kit)

Fuel Filter

Fuel Pump and strainer

Exhaust from O2 sensor back

Drained the gas

Ignition coil

PCV Valve

Tune up (plugs,wires,cap,rotor)(6 months ago)

Oxygen sensor (6 months ago)

 

 

Current Diagnostic (I am a complete amateur so some/all items could be irrelevant)

 

EGR (sticking)

Tapping/ticking started after I removed/checked this. I am pretty sure I just need to take it off again and clean or replace. I do not believe this is my main problem because I took it off, closed the valve, and reinstalled without hooking it up. This test did not change any of the symptoms listed above.

 

Distributor

I just examined the distributor and one of the plug wires and probes on the distributor was severely corroded; the rest were fine. I will get a new cap and wire tonight and check the plug.

 

Fuel Pressure

Test with a fuel pressure gauge. After sitting overnight, turn key on and I get 62psi pressure (in spec). Turn key off and it holds 25psi pressure (there is no spec that I know of for this).

While running it never drops below 50psi (in spec) even when it is acting up. While it is acting up and I accelerate the needle will sweep between 50psi to 70psi very fast.

What concerns me is that after it is acting up and I turn the key off the fuel pressure instantly DROPS to 0psi. It this an issue?

If I let the van sit for two minutes and turn the key on (pump on) then back off again it will still drop to 0psi. If I let it sit overnight it will again hold 25psi of pressure with the key off.

 

Codes

The check engine light (service engine soon) does work, but does NOT turn on. I do not get any codes. To verify I rented an “Actron Super AutoScanner” and checked the codes. I do not get any.

 

I know I can monitor real time data with this device (scanner) but I do not know what to look for (suggestions?).

 

 

 

Do you guys have any suggestions on what to try next? I am about out of ideas and I am thinking about taking it to the shop. If/when I take it in, do you have and advice on what type of shop or diagnostic test I should ask them to run (or not to run)?

[Haulin' 8.1]

Well this is what I do for a living every day and this is what I can tell you. Any one of those three problem areas you listed could be the cause. Replacing the cap and rotor is step one. I would replace the EGR because those stick open and cause these symtoms on the 4.3 all the time. If it were mine I would do this to double check the fuel system. Remove the uppper plenum just like you were going to change injectors etc., then reconnect the fuel lines to the spider block. Prime the fuel pressure with the key like you've been doing and watch for a leak. You should crank it to switch the injectors, sometime the lines leak. It should hold some pressure, if it's going back to zero instanly there's a leak, bad regulator, or the check valve on the pump is bad. If you can't see any leaks with a visible pressurized system clamp the return line off with a rag and vise grips. If the pressure sticks now the regulators bad. If it still bleed off quickly and no leaks it's the check valve. Check valve is no big deal just harder restarts.

 

Vernon

[daveg_01]

Very good call. So far it is exacally what you layed out.

 

I replaced Cap and wire, EGR. Thanks !!!

 

and....

---cut and paste---

I double checked my work on the CPI install and found a problem. One of the fuel lines was not all the way in and it was slowly leaking. I oiled (really helped) the lines up real good and made sure it was all the way in this time.

 

I gas fouled all the plugs so I have to change the plugs before I can let you guys know if that fixed it. Also, it is still bleeding off pressure with the key off. It has been going all the way down to 10psi.

 

My current guess is it is the pulsator since it was never replaced. From what I understand this might not cause problems after the van has been started.

 

I will try and change the plugs before work tomorrow and let you guys know . I might not get finished because it is not the easiest job on that van.

[daveg_01]

I finally got it fixed. I suspect it was the pulsator.

I ended up dropping the tank and replacing the pump, threw out the pulsator and replaced with fuel line, replaced the main gasket and a missing o-ring on one of the fuel lines to the tank. I am not sure if the o-ring was lost when I dropped the tank or some other time.

 

It runs great now. Thank you guys so much for all you help and suggestions!!!!!