My 99 Blazer, 4.3 Vortec (W) is getting harder to start in the morning now it's turning colder in the UK...

This morning it took about 10 attempts to get it to start, when it does it runs 100% fine. Sometimes it'll fire but not catch.

The fuel pump failed a couple of weeks back, and I replaced that with a new one.

I've also fitted the following new parts:
Distributor cap (Delco)
Rotor arm (Delco)
HT leads (Delco)
Plugs (Denso Platinum)
Fuel filter

Oil and filter

I've also done a fuel pressure and leak down test and everything checked out OK.

So, any ideas? Help please!

Sera

 

Sera, There are a lot of aftermarket fuel pumps that don't meet the necessary specifications for this engine. And, just because it's new, doesn't mean it's good Always best to inspect what you expect when replacing parts.


Did you use this procedure for checking fuel pressure and leakdown: https://blazerforum.com/forum/2nd-ge...eakdown-88305/ Post all 4 readings and we can analyze them for you.

 

Thanks. I recheck and post the result. I can't do the test at the filter yet as I don't have an adapter, but I'll get one sorted.

The problem is variable. This morning it fired straight up, first turn of the key.

It's only ever the first start of the day that's difficult, and that's not always a problem. After that, or when it's warm its always 100% OK.

 

Done a fuel pressure test this afternoon as my tester finally arrived.

Pump running, engine off 63psi
Pressure after 10 minutes (leak down) 48psi

I don't have an adapter to test at the fuel filter yet. But maybe I'll get one.

Perhaps replacing the regulator would be wise anyway as it's the original and is now 16 years old with 143k miles...

 

Might be best to gather all of the diagnostic data first, then make a decision

 

Checked fuel pressure first this morning. By using the test connector in the fuse box to turn the pump on I was getting 63psi when the engine was warm. Now, cold I'm only getting 56psi. Battery voltage was 12.5v

Leak down, after 45mins gauge shows 50psi

Removed the throttle body and had a look inside the inlet, no sign of a leaking regulator. Cleaned the tb up while it was off as it was filthy.

I don't have the parts to test the fuel pressure at the filter as I need a special adapter, I'm trying to find one in the UK.

Otherwise it's back to the pump or regulator. The pump was new a couple of weeks ago, but I don't know what make it was, expect it was a budget one though.

 

At the service port on the engine: with the pump running, engine off, your "warm" reading of 63psi is fine. 10 minutes after the pump shuts off, pressure must be above 55psi. Your "cold" reading of 56psi is too low. Whatever is causing that reading to be so low, is causing your hard start when cold. There is definitely a problem with the fuel delivery system, but without knowing what the readings are at the fuel filter, there is no way of knowing what, or where, the problem is.


As for the parts to build the adapter in the link: A good hardware store, or plumbing supply, should have the parts to build the adapter. You might end up using metric pieces. For the Dorman fuel line parts, your auto parts store might have to order them.

 

Dorman isn't a recognized brand in the UK, people in the parts places would look at me like I'm mad - I know you can get their parts everywhere in the USA.

I've ordered the parts from Rock Auto to make an adapter.

If it does come to a new pump, anyone tried just replacing the pump itself with one of these? http://www.ebay.co.uk/itm/361117118582