Okay like I said in a previous post it's an '86 Iroc with 305 TPI that starts fine in the mornings and when hot but if it only sits for a minute but if it sits for very long it just cranks and cranks before it hits.
you said you had the same problem and got rid of your cold start injector(I checked mine and it didn't leak) and oil pressure switch, I unplugged it and nothing changed...but if i jump the wires that go to it my fuel pump comes on with no signs of shutting off. is this right????
what else can I check?
thanks

 

does your fuel pressure drop to zero right after you shut the engine off?
if so, then you may have a bad regulator.

So you bypassed the oil-pressure safety switch and the problem is still there?
that's right the pump should run.

In the end I ran a larger inline pump, my own relay & wires to the pump, plugged off all the exhaust crossover/EGR, PCV, and the cold-start injector-removed. The problem went away but I think now that I probably had a bad regulator, or may have been ECM related.
I did run my engine at 160F or less most of the time, so it could have been too much start-up enrichment flooding it.



[This message has been edited by The ODB (edited March 03, 2001).]

 

hhmmm I run mine with a 160* stat too.
I don't have a fuel pressure gauge but I will soon. How can I check my regulator?
what should I look for when I get my pressure gauge? And should I leave the oil pressure switch unplugged?
Thanks a bunch man.

 

ttt

 

I doubt a bad regulator would look any different on the inside or out than a good one, so I don't know how you'd tell.

watch the pressure gauge when you turn the engine off. Look to see if it holds fuel pressure or it drops like a rock.

If you know the oil-press switch is not the problem then there's no reason not to plug it back in.

If everything is good, then the low thermostat might be making you too rich at warm startup. Ask Glenn exactly what would happen to cause that and a possible solution.

 

JB,

The auxilliary oil pressure switch is apparently working fine. As long as the fuel pump/ECM fuse is good, jumping the wires at this switch SHOULD cause the pump to run. This is completely normal.

The colder T'stat shouldn't be causing a real problem on warm restarts (after heat soak). The cold start subroutine will only enable if the coolant is below 40°C (104°F) and the MAT sensor is within 10° of the CTS reading. The reason for this is that a warm engine sitting in cold air (more than 10° difference) still doesn't need extra starting fuel. So unless your T-stat is allowing the coolant to drop below 104°F, the cold start enrichment routine shouldn't be a factor. Of course, this is all presuming that your CTS sensor is working properly. I wouldn't think a 160° stat would do that, and am still betting on leaking injectors or a regulator.

Additionally, a regulator that is leaking down won't cause enrichment unless the pressure control diaphragm is perforated and allowing fuel to be pumped through the vacuum hose and into the plenum. The easiest way to eliminate that possibility is to remove the vacuum hose and observe the regulator while the engine is running. If you have fuel spewing out the vacuum hose bibb, you have a leaky diaphragm.

If the regulator is simply leaking internally (back through the fuel return hose to the tank) the fuel pressure would drop quickly after shut down. If you suspect this, turn the ignition to RUN and wait a couple of seconds before cranking to allow the fuel pump to build rail pressure. If the engine still requires excesive cranking to start, you're not lacking fuel, but are already too rich.

Your description of the symptoms is almost a textbook example of injector leakage. After allowing the engine to sit overnight, the extra fuel has a chance to evaporate out, and the extra fuel left over actually assists the cold start routine. Also, allowing it to sit for a few minutes after hot shut down has no adverse effects, since not much fuel has been allowed to leak into the chambers, so it restarts normally. Allowing it to sit for twenty minutes causes excessive cranking, since all of the fuel in the lines and rails is allowed to leak down into the chambers, causing flooding. Classic example of leakage. If you don't get leakage through the regulator diaphragm, there's not much left but the injectors.

As the ODB suggests, a pressure gauge will be very helpful in diagnosing this. If you don't have a fuel pressure gauge, you can use a refrigeration gauge manifold and the low-side gauge. Just drain and vent the hoses and manifold when you're done so you don't contaminate any refrigerations systems you might connect to.

------------------
Later,
Vader
------------------
"No matter how hard you try you can't stop us now..."

 

Vader, the CTS is new.
Okay I'm gonna check the fp regulator since I recently sent my injectors to cruzinperformance to be rebuilt.I'll pull that vacuum hose today and see if fuel is seeping in that way.

 

Okay new update I just went out there and started it and then just stuck a screwdriver with a towel around it in the scrader valve and .........nothing....just moments after it was running....is it possible I reinstalled my injectors incorrectly after rich rebuilt them???
no signs of fuel in that vacuum line.
Thanks for the time with this guys.

 

ttt

 

John,

First, you DID change the fuel filter and flush the lines before installing the cleaned injectors, didn't you? Rich usually reminds all of his customers to do that as a precaution to avoid trashing a clean set of injectors. I just had to ask...

No fuel coming from the vacuum line to the regulator should mean that the regulator is not leaking externally. It might still be leaking down internally - allowing all pressure in the fuel rails to be relieved back to the tank through the return hose.

One way to eliminate this possibility is to securely pinch the fuel return line with a 'C' clamp and soft wood blocks (to prevent damaging the hose) or with the special Vise-Grip pliers with rounded jaws made specifically to crimp hoses.

Once the hose is pinched, turn on the ignition again for a couple of seconds. You should hear the fuel pump run. Turn off the ignition and check for pressure at the Schrader valve again. If there is now pressure present, the regulator was probably leaking back to the tank. This means you get to remove the plenum again to replace the regulator.

If the pressure is still not present, the fuel rails have leaked down through at least one injector, or are leaking externally, or the fuel pump check valves are failing. If the pump valves are failing, it's likely that your operating fuel pressure is lower than it should be. This is why a fuel pressure gauge is so valuable in testing this type of problem. If you can read an actual pressure, it may be a hint as to exactly what is happening.

Sorry it took so long for a reply.

------------------
Later,
Vader
------------------
"I'm'a do Things My Way - It's My way or the Highway."
Adobe Acrobat Reader

 

Vader,
I replaced the fuel filter some time ago when I got the car.So, I spent the whole afternoon yesterday removing my plenum for an experiment...I unbolted the fuel rails and lifted them enough that I could see the tips of my fuel injectors, then jumped the wire that goes to the oil pressure switch to engage the fuel pump...I took some moving and shaking but I got to see all injectors while the pump was on.....NO LEAKING.so there goes that.
now on to the regulator.if I'm looking down on it from the front which hose should I clamp?
Thanks again.

 

Okay I figured out where to clamp the return line. With that clamped down the fuel pump sounds like it's bogging down,nothing like before...wait a few seconds then check the scrader valve...nothing well a slight trickel of fuel this time.nothing under pressure though,soooo what's left anyway?
the fuel pump? could that cause this problem?

 

I'm sure everyone's tired of seeing this post but.....

 

JB,

Back to the front....

It is becoming very apparent that you need to beg/borrow/buy a pressure gauge. All you really need is a short hose with a Schrader valve connector and a 0-100 PSI gauge. Make sure the hose is rated for use with fuel and for at least 100 PSI working pressure. Test the pressure with the pump running, then monitor the pressure as the pump is turned off.

By your description of the pump noise when you blocked the return line, it sounds like the pump is moving fluid and making good pressure. Unfortunately, it sounds like the regulator may be leaking it all back to the tank. A gauge is the sure way to diagnose the problem, but the regulator is getting more suspect all the time.

------------------
Later,
Vader
------------------
"I'm'a do Things My Way - It's My way or the Highway."
Adobe Acrobat Reader

 

Incidentally, I don't think anyone is tired of the problem. We're in it this far, so I think we'd rather see a happy outcome and some conclusion to the problem.

Good luck.

------------------
Later,
Vader
------------------
"I'm'a do Things My Way - It's My way or the Highway."
Adobe Acrobat Reader

 

If you clamped the return line and left it clamped, and it was shut of totaly so nothing could flow through it. Then ran the pump and shut it off, and you had no pressure then, it would not likely be the regulator. the regulator returns fuel through the return line that you pinched off If it s pinched off it wouldn't be able to.

It would be the pump leaking off, and/or not making enough pressure to begin with.

If it isn't bleading off through the return line, and it isn't leaking through the injectors, and it isn't leaking through any fittings to the atmoshpere, then it has to be losing pressure back through the feed line. Either through the pump or the rubber hose or pulsator that attaches the pump to the hard line.

You really need a fuel pressure gauge if you are going to succesfully work on this type of car. It would show you in a matter of seconds what was going on.

------------------

Tracy /AKA IROCKZ4me
'86 IROC-Z Camaro
"Cogito ergo zoom"

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• Nitrous Express nitrous oxide

My IROC-Z
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[This message has been edited by IROCKZ4me (edited March 07, 2001).]

 

I've had this same problem for quite awile too.
If the pump check valve were bad, I would think that it shouldn't be hard to start if you turned the key to the "On" possition for a couple of seconds to build pressure up before trying to start.
I've had my injectors serviced and I still have this problem too.
For some reason I've got a hunch that the cold start injector is too blame on mine but that is pure speculation.

Bob

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350 TPI, 700R4(rebuilt), K&N's, MSD 6AL, Headers, Flowmaster, 160* stat, airfoil, MAF screens cut out. 13.88 @ 101.18 mph

 

Okay, okay I picked up a pressure gauge today. I sure will miss dobbing around in the scrader valve with a screwdriver though(never knew what to expect).
seriously, with the key on for the first few seconds when the fuel pump is on the pressure goes up real good like 40ish hard to tell because as soon as those first few seconds are up the pressure drops back to 0.
But with the oil pump switch jumped so the pump runs constantly it shows 46#'s
then when it's up and running it goes 36#'s which is in spec with my haynes manual.
thanks.