1993 starting problems - and where is the darn fuel pump relay?

[Megs1082]

Hey guys. My wife's 1993 Jimmy is having the dreaded starting issues. She's got the 4.3 liter vortec CMFI 4x4 version.

It developed over the course of a month or so from easy to start to hard to start. Now in order to get it to start you have to try for a couple minutes or hook it up to an external secondary car battery through jumper cables to get it to start or as I just found out last night you can toggle the ignition key about 5-6 times and kick the starter off in quick fashion and it'll start several times into these attempts.

I've replaced the plugs, checked the wires, replaced the distributer cap, changed the fuel filter, and checked all the fluids before I really started getting concerned.

I bought a fuel pressure guage and hooked it up to the schrader valve to see where my fuel pump pressure was according to the Chilton manual recommendation. The pump hits 60ish and then - SOMETIMES drops off to below 50(1 in 5 times) but usually holds at 55. When the car is running it hovers at about 55-57ish.

I've had the alternator, batter, and starter all checked out at autozone - they are all tested good. I would think this was a weak battery because of the fact that whenever I hook up a set of jumper cables to a second vehicle cables it will start in the first or second crank. However - yesterday I swapped a 900 cranking amp battery from my Grand Prix(the car we were attaching the jumper cables to) into her Jimmy and put her 700 cranking amp battery in my Grand prix. The same problem stayed with the Jimmy even with the switched batteries. Now here's the odd part. When I reconnected them via jumper cables ==== whalla! instant start! The voltage doesn't change on the jimmy's guage when I connect the two? It just doesn't make sense. It's almost as though the Jimmy needs (900+700) 1600 cranking amps to start normally??????

After reading this forum a bit it looks like a lot of people have this problem, but I've not yet found a solution.....it looks like it could be several things, but I'm wondering if it's not the fuel pump relay - -- - as in it's not charging correctly.

Follow me here. In the Chiltons manual, it states that under prolonged engine cranking without starting the engine the oil pump relay will override the fuel pump relay's "off status" and will engage the fuel pump. That explains that fact that if I just let the jimmy turn over for 2 minutes it'll start. (battery and starter won't handle this on a routine basis so this isn't a solution) and it might also possibly explain why if you crank it in short fashion about six times it will start. Because one of those times that fuel pump relay gets charged or cumulatively gets charged and then it fires off the signal. I still don't understand the extra amperage starting the car....but something must be tied in with that somewhere.????.

Another oddity is that the fuel pressure drops sometimes, doesn't drop other times. The one key thing is that once it starts one time....It will start easily until it gets cold again - which makes me think it must be some sort of relay somewhere?????

I'd like to change the fuel pump relay, but I don't know where that is???? It says in the convieniece center in the middle of the dash but I see no such thing??? Any ideas? We couldn't find that fuel pump relay behind the glove box panel, and I don't see a convieiniece center anywhere like the chiltons says near the center of the dash, nor under the center console area?????

Any ideas where this fuel pump relay resides?



If it's not the fuel pump relay does anyone have any solutions or other suggestions to try?

[Megs1082]

Despite the chiltons saying the fuel pump relay was behind the dash and the GM dealership saying it was on the drivers side wheel well, we eventually found the fuel pump relay on the drivers side firewall. We tested to make sure it was the fuel pump relay by unplugging it and turning on the ignition and we got no fuel pressure, so we know it's the proper piece. We replaced it with one from autozone to no avail....is there anything anyone else can think of???? We ran it by a service manager from the GM dealership and he didn't say much.

[Megs1082]

it is a jimmy 4x4....

I still can't figure out the problem. Replaced the Fuel pump relay - no change. It's getting worse I can't start it at all now practically.

I took of the intake air/fuel cylinder thing - and peeked inside. It did NOT smell gassy. I attempted to start the car as well as just turn the key to where the fuel pump went active, I could neither hear nor smell gas leaking. So I don't really think this is a fuel regulator or intake "area" problem.

Fuel pump the next bet?

[Megs1082]

I took off the upper manifold, there is fuel sitting in the bottom of the fuel pump regulator side. This could be a problem. I'm not sure what this means...

Here are a few pics. Does anyone have any thoughts?

http://www.geocities.com/jvonengeln/gmc.jpg

http://www.geocities.com/jvonengeln/GMC2.jpg

http://www.geocities.com/jvonengeln/GMC3.jpg

[jdmccright]

Fuel should not be pooling in the manifold...it should be going through the spider assembly and to the poppet valves. This means a leak somewhere...either the spider tubes to the poppets or the regulator or nut kit. check all the connections for leaks, the tubes for cracks, and the connections to the poppets and the central assy. Whichever side it's pooling is where you should look.

[wb8yjf]

Last time I saw that in my engine, the spyder (injector) assy. was leaking & needed replaced. I was also told that this is a potential fire hazard...

[Megs1082]

I replaced the fuel pressure regulator - put it all back together and am having the same issue

Guys,

I need more advice......I tried a couple more things I need to report on.

I took a voltmeter and checked the voltage at the battery when the car is trying to start. It never drops below 11 volts and the battery sits normally at 12.4ish. The reason I checked this is that one guy said when the starters begin wearing out they suck up a lot more amperage - if they suck up too much amperage they will drop the voltage on the battery. If the battery voltage drops to less than 9 or 10 volts sometimes the computer won't function right and so it won't start because the computer is not acting correctly - This would explain why the car runs good when it actually is running because the battery is at 14.4 volts and so supplying enough juice to let the computer run perfectly. ALAS, this is not my problem nor a fix because my voltage never drops below 11 volts.

I checked a couple other things. Someone suggest a fuel pump volume test. They said the fuel pump here should put out about 1 quart of gas in 30 seconds. I'm not sure how scientific my test of this was because I'm not sure that the schrader valve/pressure fuel gauge release button allows full flow, but I tried this and let the car try to start with the fuel pressure gauge attached to the schrader valve and the bypass hose hooked up. I only gathered 10 ounces in 30 seconds. LIke I said, I'm not sure this is accurate because I don't know if the bleed valve on the fuel pressure gauge is of a diameter to let full flow out, BUT that 10 ounces is low compared to the 32 ounces it should have????.

3rd test -- Someone else said that I should find a point along the fuel lines with rubber hose. Turn the key to the ignition point (1 click shy of starting to where the pressure builds, and then turn off the key. Then pinch the hose and have another person check the fuel pressure at the shcrader valve. If the pressure remains the same at the valve you aren't leaking on the engine/injector side, and if it drops you are. Likewise, after a couple minutes, when you release the pinch, if the fuel pressure at the guage drops really low it means the pump isn't holding pressure in the tank. This is what happened. I pinched the line when the pressure guage read 57. I held for two minutes. The line pressure dropped to about 56.5. I released the pinch after about 2 minutes and the pressure dropped to 30ish PSI. That seems to point to a bad/dying fuel pump???

Do you guys agree? Any other tests I can preform to verify it is a pump before I drop the tank? What else should I replace besides the fuel pump while I've got the tank dropped?

[Megs1082]

We're trying to buy parts today; any other parts we should buy besides a fuel pump? What about a pulsator check valve - someone on another forum said that's what it could be, but we can't seem to find that part? If it could be that valve, how do we figure out if it is the pump or just the valve?

[wb8yjf]

For all the work you have to go thru getting to the pump, replace the pulsator anyway. It's about $20 at Autozone. I hear that it is either the type I have (an oval thingie) or a piece of tubing and is located between the top of the pump and the line going out of the sender - you'll know which when you get to the pump. Mine had bad seals on top & bottom where it connected to the line.

Have fun...

[old_master]

You're making yourself crazy thinking too hard
Cycling the key several times or using a jumper battery will allow the fuel pump to build slightly higher pressure. Your fuel pump relay is working fine. Fuel pressure on a 4.3L is almost a "digital" thing and by that I mean fuel pressure needs to be a MINIMUM of 60 psi when it primes, (key on engine off). After approximately 2 to 3 seconds, the pump will shut off and fuel pressure must remain above 55 psi. If the fuel pressure holds, there are no leaks. If the fuel pressure drops below 55 psi, repair the leak(s) and retest.

[Megs1082]

all my fuel lines were corroded in the back by the fuel pump. Two of the lines broke, so I had to buy some injector hose and cut the wires out with a greased hacksaw through gasoline (greased and SLOW so I didn't blow up).

I replaced the lines with $3.50 per foot injector hose - ($40 bucks--

anyway I started the car with the tank on the ground and it started FIRST TIME!

YAHOO!

Now- I spent the next 3 hours trying to get the tank to go up and gave up in utter frustration. I've about broken the sending unit at this point by bending the top and trying to get room enough to connect all the lines. Is there any tips to getting the fuel tank back up there? This is one of the most horribly annoying things I've ever tried to do on a car - ranks right up there with chaning out a set of old mannifolds that all the bolts were rusted and kept breaking off.