95 Blazer hard cold start.

[JA no Y]

I have a 95 Blazer that has become VERY hard to start when cold. Once it is started, it runs fine. Once engine has warmed up, it starts just fine. I thought it needed a tune up to help the hard starting, so I replaced the fuel filter, spark plugs, plug wires, distributor cap and rotor button. Still had trouble starting when cold.

Next, I checked to make sure I had adequate fuel pressure. I knew it took more fuel pressure to start than it took to run. I had to have 58 to 65 psi fuel pressure to start, and the pressure would drop 3 to 10 psi when running. So I checked pressure at the test port, and was only getting ~50psi. That explained the hard starting and why it ran once I got it to start. I replaced the fuel pressure regulator, (since it was easier to get to than the pump) no change. I checked the pressure at the input of the fuel filter, 50psi.

So now I'm wondering if it's the pump or the fuel sending unit. I've never had a pump have low pressure like this. They've always either worked or just craped out on me. The pump "seems" to be working.
Could my pump just loose pressure like this? Or could my problem be in my sending unit? If my sending unit is bad, how can I accurately check the pump, and vise versa?

[Tech II]

I believe you need 60 psi to start on a cold engine.....since you have replaced the fuel filter, I think you need a pump.....

Not sure if you have a fuel module setup(very expensive) or a fuel sender with a fuel pump($70) that is replaceable....

If it's plastic line coming out of the top of the tank, it's a module....if metal, it's a sender and pump....

[JA no Y]

It's the sender with the metal lines, so I can just change out the pump itself. Just never had a pump give low pressure. They've always just completely given out and not work at all.

[Tech II]

See this a lot on 4.3 engines...when the fuel pressure is marginal, the first thing you do, is replace the fuel filter...if that doesn't fix the problem, and it starts if you give it a "shot" of carb cleaner, then it's usually the pump.....

One other problem I have seen, and should be checked before replacing the pump, is chassis ground for the pump......

[JA no Y]

Well, not sure if it was the fuel sending unit or the pump that was the problem. Fuel line coming out of the sending unit was rusty and got damaged during removal, so I had to replace it also. Put new pump and sending unit in, tap the key...starts right up. Just thankful I waited till the tank was almost empty to drop it.

[Tech II]

Sending unit has nothing to do with pressure, unless it was leaking......

[andymikem97]

Not to hijack, but I have a '96 Jimmy with the same problem. If it's started EVERY DAY it will start hard, but it will start. Let it sit for a few days, and it will turn over and "try" to start, but won't catch. Put just a light squirt of starting fluid in it, and she fires right up and purrs right along. And the previous owner had just put a new fuel pump in it right before we bought it. I hate to think it's a bad fuel pump, but it likely IS a cheapy pump.

[j cAT]

Originally Posted by andymikem97

Not to hijack, but I have a '96 Jimmy with the same problem. If it's started EVERY DAY it will start hard, but it will start. Let it sit for a few days, and it will turn over and "try" to start, but won't catch. Put just a light squirt of starting fluid in it, and she fires right up and purrs right along. And the previous owner had just put a new fuel pump in it right before we bought it. I hate to think it's a bad fuel pump, but it likely IS a cheapy pump.

look any problem like this just check the fuel pressure with a gauge . doing the test procedure you can figure out if its a pump problem or the regulator/injectors.

do not forget about proper voltage to the pump and good solid wiring for pump power.