starting

mudtaxi · Post by **mudtaxi** » Thu Dec 27, 2007 9:10 am

ok i have had a problem with my truck since i changed the motor it was a used motor with 50,000 miles the problem is that it starts with ease when it is cold but once it warms up i have to turn it over a few times before it with start i have change my cap and rotor cuz the old was fried i have checked vacuums any ideas as to what it might be

Post by **HenryJ** » Thu Dec 27, 2007 9:18 am

I would start with the Fuel System Diagnosis seeing as you have addressed the ignition system.

mudtaxi · Post by **mudtaxi** » Thu Dec 27, 2007 9:35 am

i can hear the pump and i have not noticed any leaks of odor of gas. so could it just be a dirty fuel system or fuel filter? but then i think about it how would it being warm affect the fuel system or filter.

barch97 · Post by **barch97** » Thu Dec 27, 2007 10:46 am

Fuel filter is only about $10 and takes all of 30 seconds to replace. I'd give that a try.

Post by **HenryJ** » Thu Dec 27, 2007 11:03 am

The warm part is a tough one. Heat can create resistance. That relates to electrical problems usually. The fuel pump is electrical, as are ignition components.

Do the easy stuff first. If it has been over 15k miles, or a year since you replaced the fuel filter, that is a great place to start. it needs to be done.
The fuel system can be diagnosed pretty easily. Pressure checks and leak down rates will speak volumes. The regulator may function poorly when warm, or the fuel pump? Worth checking.
The cap and rotor can be fouled quickly. They are always worth a check, plugs too. Ignition modules have been known to operate erratically with differences in temperature. There are lots of places to go.

roadrunner · Post by **roadrunner** » Fri Dec 28, 2007 2:25 am

If you don't find anything electric giving trouble I would suggest looking to the injectors. Perhaps the set on the motor now are older than 50k? I recently had to replace a full set on my car that passed leak-down and pressure tests. Problem was after a 15-30 minute hot-soak (time from hot shut-down to next restart) I would have to wind on the starter excessively for restart. Reman injectors solved the problem and picked up mileage a little too. Apparently all were seeping just enough to cause over-rich hot restart condition. Check all else first though even reman wasn't exactly wallet friendly.

Post by **HenryJ** » Fri Dec 28, 2007 6:08 am

A good point. We have been relating this all to the crew cabs engine. Perhaps he is working on an earlier model? Maybe a mid ninties CPI engine with the nut problem?

Specifying the year make and model my help.

mudtaxi · Post by **mudtaxi** » Fri Dec 28, 2007 8:18 am

2004 gmc sonoma zr5

Post by **HenryJ** » Fri Dec 28, 2007 8:47 am

Not a nut problem. This should be the MFI style injectors, so sticky poppets is not an issue.
Results of the fuel system tests will be helpful.

mudtaxi · Post by **mudtaxi** » Fri Dec 28, 2007 9:53 am

where can i get the guage and how much does it cost

Post by **HenryJ** » Fri Dec 28, 2007 11:01 am

Did you change the fuel filter? replacing fuel filter

killian96ss wrote:
wamason wrote:How do I check fuel pressure?
Well first of all do you have a screw on type fuel pressure gauge? If you do you just hook it up to the schrader valve, and make sure you either let the truck sit overnight or just relieve the fuel pressure yourself by putting a rag over the schrader valve and lightly press down to relieve the pressure. The schrader valve looks like a tire inflation valve. Once you bleed off excess pressure hook up the gauge, start the engine, and observe the reading. You should get 60-66 psi. If your gauge has a bleed valve make sure you bleed off some fuel to help trapped air escape. This will give you a more accurate reading. The schrader valve is located near the rear of the drivers side valve cover. Here is a pic for reference.

killian96ss wrote:This is the one I'm using. I only paid like $30 for it at Pep Boys. It is made by Actron, Part # CP7818.

mudtaxi · Post by **mudtaxi** » Fri Dec 28, 2007 11:59 am

no i havent changed my filter and yes i have the valve going to try and change it this weekend

mudtaxi · Post by **mudtaxi** » Fri Dec 28, 2007 12:03 pm

could it be a throttle position sensor as well

roadrunner · Post by **roadrunner** » Fri Dec 28, 2007 3:48 pm

Many electrical possibilities. If you don't have access to an OBD II scanner stop by an auto zone or advance auto parts and they can scan it for you. They generally will do this for free. This could help you eliminate any possible fault codes and the troubles they might indicate. Just another step in the diagnosis procedure.

mudtaxi · Post by **mudtaxi** » Fri Dec 28, 2007 5:40 pm

well i have done that and all it says in random or multiple misfire

Post by **HenryJ** » Fri Dec 28, 2007 5:50 pm

Check the fuel system. That will tell volumes.

rlrnr53 · Post by **rlrnr53** » Fri Dec 28, 2007 7:36 pm

A co-worker had this problem week or two ago. after changing plugs and wires, we used the old method of spraying water on the exhaust manifold to see which cylinders were not firing. After checking, we determined that four cylinders were not firing right. No's 1, 2, 7, and 8 were not heating up as much as the other four. The trucks owner told us that he had changed the cap and rotor, and had cracked the distributor in the process. After installing a new cap and rotor, and using a small screw and nut to pull the cap down tight, the miss disappeared.

F9K9 · Post by **F9K9** » Fri Dec 28, 2007 8:05 pm

Would I be completely out of line to suggest a starter? I know that in my youth that a warm starter (in early stages of failure) would not crank as fast when hot. Hopefully technology has corrected that issue. Just a stab in the dark.

roadrunner · Post by **roadrunner** » Sat Dec 29, 2007 3:36 pm

mudtaxi wrote:well i have done that and all it says in random or multiple misfire

Checked your wiring to the O2 sensors? Last time I had this multiple misfire/random misfire I had damaged wires at bank two sensor one. Apparently shorting together intermittently. And no it didn't throw a code for the sensor being bad either. Also you might try cleaning your mass air flow sensor. I know these sound off the wall but I have experienced some really odd problems

with my CC and that's why I'm suggesting them. f9k9 makes a good point also.

Observe voltmeter during cranking or have someone hook one onto the battery while cranking and observe voltage drop level. If Battery drops below 10 volts after brief crank time (during cranking effort) then either the starter is drawing excessively or the battery is getting weak. Also make sure battery cable connections are clean and tight and cables are in good condition and haven't been replaced with undersized guage cable. If ya need a new battery remember the old rule of thumb, get one as big as will fit. In the case of batteries bigger is definitely better.

Good luck!